B&L Photomicrographic Apparatus V: System II

A Re-design

The System II represents a fundamental change in B&L integrated photomicrographic cameras. Sleeker than the early DynaZoom camera but far more substantial than the later versions, the System II is a step back to the design principles that required a focusing system. It was necessary for the System II to feature a focusing lens system because the unit was intended to be a new universal device for all (camera ready) professional B&L lines, including the earlier DynaZoom/DynOptic lines. Despite maintaining the compatibility of the system with earlier stands, once more the camera backs required are not compatible with previous versions (although they do come in all previous formats).

New Features

The opticians behind the System II seemingly asked themselves ‘how can we make this the last camera a microscopist will need?’ and set about answering it. The systems chief major departure is the coupler, specifically its diameter. At 7/8ths it’s a full quarter inch larger than the previous model DynaZoom camera, and a return to the large size used with focusing DynaZoom cameras. Care was also taken in the design of the coupler, it was made to be removed and a number of versions of the coupler were made, some making allowance for the use of a manual exposure meter.

Once more the camera back attachment point was redesigned. The new male dovetail fitting was made a bit smaller than those used previously and unlike previous models did not feature an alignment screw that required the female dovetail camera back be fixed in relation to the camera. Additionally, where earlier camera backs used two thumb screws the new versions used only one; making it a simple thing to orient the photosensitive surface however one wished without being forced to suffer an inconvenient shutter release or winder position.

Couplers and Camera Backs

Three couplers are known of: the silver Bal-Coated male dovetail, the black lens-less male dovetail, and the eyepiece mount. The silver dovetail makes good use of a Bal-Coated lens to eliminate errant reflection which can prove frustrating with uncoated optics and both it and the black dovetail carry a small slot in the dovetail that mates with the camera. This slot may be turned to align with a similar slot in the System II or turned so as to exclude all light. The purpose of the slot is to permit the insertion of the B&L Cat. # 421240 exposure meters sensor.

Versions

The versions are discrete rather than explicit, which is to say there is not any particular model number to distinguish them that is official but they are readily identifiable. One sort is focusable from below 3x to over 10x. On these models only four magnifications are marked: 3x, 5x, 7.5x, and 10x. Two versions of this sort are known, one having an all black shutter speed selector and the other having a silver ring. An additional version, and perhaps more desirable (if less common) one has the same range but is marked in one unit increments from 0-25x with every fifth mark being numbered.

Accessories

Apart from the previously mentioned camera backs a number of accessories were produced. Special viewfinder adapter plates and eyepieces were available for the various camera backs. It should be noted that these eyepieces were not the film area viewfinder eyepieces that would show the field that would be covered by various popular film sizes. Extension tubes were also available that would extend the distance between the final lens element of the shutter assembly and the camera back. Tubes were made in 2.5x and 5x lengths were produced and could be used in various combinations where special needs required.

Notes:

∗It should be noted that the connection to the shutter in all cases is a male dovetail and the designation here refers to the connection to the microscope photo-port.

†I’ve seen one in use during the course of a museum visit although I’d be hard pressed to say if it were an actually B&L item or the product of a machinist and a tight budget.

Advertisements

B&L Photomicrographic Apparatus III: Integrated Cameras

Microscope Stand Design

Around the halfway point of the last century (1940 or so) microscope design began to change drastically. Modern manufacturing and engineering, together with the proliferation of compact, bright, electric lamps contributed to an opticians ability to design microscopes which provided a new option for the photomicrographer. Contemporarily advertised as tri-nocoular (but more properly referred to as photomicrographic) microscopes began to become available with specialized camera ports that did not require interchanging a binocular body for a monocular body, or the occupation of a standard eyepiece tube by a cumbersome attachment camera.

At the time this was a considerable advance and as photographic process became more accessible and streamlined so too did the process of making ones microscope ready to capture an image. In many cases a microscope could be used visually as normal and simultaneously outfitted with appropriate apparatus capture images on a variety of media. Ones microscope could stand ready for either photomicrography or visual use and a great many sights that were only previously fleeting could be captured.

Regrettably, while some mechanical aspects such as the Royal Microscopical Society (RMS) thread, or 23.2mm eyepiece have become standard, the same can not be said of photomicrographic apparatus. For obvious reasons apparatus from one manufacture may not be compatible with another. Infuriatingly, apparatus from a given manufacturer may not be immediately compatible with a different line or generation of microscopes.

The Systems

It can be impossibly difficult to find information on the integrated camera systems of Bausch & Lomb, so forgive any inaccuracies and permit the establishment of two broad categories; the DynOptic/DynaZoom (hereafter DynaZoom camera) and the Integrated Camera System II (hereafter System II). Each was available with a range of formats and in a variety of styles with various interchangeable or permanently fixed accessories.

The DynaZoom camera was created specifically for the so named line of microscopes and was available throughout the life of that line. When the black finish stands were replaced by the slate finish models the cameras followed suit but maintained the established standards and are interchangeable with the earlier versions and vice versa.

The System II was in simultaneous production with the DynaZoom but was created so as to be compatible with a wide range of microscope lines and to offer improved options and forward compatibility. While still compatible with both the black and slate DynaZoom microscopes it could also be fitted to StereoZoom, and BalPlan microscopes as well as Bausch & Lomb Bench Metallographs, and inverted microscopes. System II also saw the introduction of automatic shutter control with electronic light metering.

One may immediately identify the camera system because in the DynaZoom cameras of every sort there is no independent magnification (focus) control. System II cameras of every sort feature a vertically oriented magnification (focus) control which may be marked from 0 too 25 or from 3x too 10x.

Sorry for the long silence, computer failure and a new job have eaten up a great deal of my time lately. I promise the next post wont be so far away. -K

B&L Photomicrographic Apparatus II: Attachment Camera

The Attachment Camera

The attachment camera as designed by Bausch & Lomb remained primarily the same over its production life. Changes to the apparatus itself were minor and all components have proven interchangeable if one is faced with assembling a complete working device from multiple units purchased separately for parts. The shutter features the following speed settings: 1/10, 1/25. 1/50, 1/100, 1/200, B, and T, and uses a standard cable release. There is no prism release as may be found on attachment cameras from other manufactures. This is a bit of a trade off, as without the prism release one can not direct 100% of available light to the camera. Fortunately, absence of a prism does eliminate its motion as a source of vibration during exposure. In place of a swing out prism a preferential beam splitter is fitted which directs 85-90% of available light to the camera and from 10-15% to the viewer. Aside from the camera itself (see below) the part most likely to be missing is the ocular sleeve which is a metal collar that slips over the tube of the microscope prior to the fitting of an ocular. The sleeve holds the shutter assembly in alignment with the optical axis of the microscope and holds the beam splitter at the exit pupil of the ocular.

This design requires a vertically oriented microscope tube. If used with a classic style B&L Dynoptic binocular microscope one will need to obtain the interchangeable monocular body. When attached the viewfinder projects horizontally towards a seated microscopist. There are two varieties of viewfinder both projecting significantly from the axis of the microscope so that the microscopist need not lean in uncomfortably when using the camera. Each sort makes use of a ground glass screen which the older version views through a large fixed focus condenser. The newer variety uses a spiral focus condenser that improves the clarity which one obtains to a certain extent, but does require that the user lean in towards the lens for proper viewing. Focus is entirely via the controls of the microscope.

Cameras

The camera bellows and bodies that are available for the unit run the gamut. Most common of the camera attachments is the 35mm camera body. The camera itself is often quite diverse and might be any of a half dozen different models. As of this writing the author has found the following 35mm camera bodies: Argus (stripped down, unknown model), Kodak Pony (without view finder), Kodak ColorSnap (complete with permanent lens mount). There are two lengths of bellows tube for the 35mm camera, one providing a 5x enlargement, the other 10x. Each tube is equipped with a dark slide.

Less common is the 2¼ x 3¼ cut film holder which is not equipped with a dark slide. The fixed enlargement factor metal bellows cone is felt lined internally and is confirmed as compatible with Kodak film holders and plates. There may or may not have been a ground glass focusing screen but considering the standard size of the film holder it is simple enough to obtain one from a third party source. Thankfully, a ground grass screen is not necessary as the film plane is parfocal with the fixed focus ground glass viewer. Film is only infrequently available from a limited number of suppliers but may be desirable if one has access to a dark room and a willingness to cut down more commonly available film stock. It is not compatible with the common 120 roll film Graflex camera backs without modification to the camera back or a homemade light seal.

The 2¼ x 3¼ Polaroid instant film pack camera backs may be found and makes use of the 10 exposure peel apart film now produced by Fuji. Although the images obtained are very nice, and provide an easy introduction to medium format photomicrography, the difficulty of pulling film from the camera (so that the chemistry is applied to the film) will require verification of alignment between exposures. The commonly available backs compatible with Graflex cameras are not compatible with the above described bellows. An additional model permanent camera is fitted to a plastic fixed enlargement factor bellows cone and is not outfitted with a dark slide. Unless one has a Polaroid back that is known to be interchangeable with a Kodak film holder it is advisable to obtain the permanent Polaroid version if one is set upon using that format.

The 4 x 5 camera bellows is infrequently seen but provides the best option for those interested in medium or large format photomicrography. A scaled up version of the 2¼ x 3¼ camera, it is metal and felt lined and like it’s smaller counterpart, also does not have a dark slide. The cone is compatible with 4 x 5 camera backs, of all sorts including cut film, film pack, and plate holders. Off the shelf 120 roll film backs from Graflex are compatible and the ease of using such a system can be an economical way for the beginner to get involved with large and medium format chemical photomicrography. Depending on the winder it may be necessary to remove the metal spring that holds cut film plates in place. Ground glass focusing screens are simple to find or make with a bit of glass and a dab or carborundum grit, but the original screen features a thick rubber frame.

Use

No doubt everyone can picture the attachment camera in use on a classic monocular microscope. In the interest of displaying something one might not have considered, below is an image of the attachment camera (with Polaroid back and spiral focus viewfinder) in service on a Phase Contrast DynaZoom as well as two detail images of the difficult to find ocular sleeve.

 

Notes:

∗Images in reference works term the apparatus the “Model N” attachment camera but I have not been able to locate the appropriate B&L catalog or manual to confirm the proper name.

†The camera back is slightly too wide and thick. A few minutes with a hobby grinder or similar tool is all that is needed to permanently adapt a roll film back. If one is unwilling to dedicate a camera back, a thick felt gasket may be glued to the back and cut so that it projects slightly into the bellows cone to prevent it from being jostled while in use.

‡The hardest part is cutting the glass to the right size and it isn’t even that hard if one has ever cut glass.

On Photomicrographic Apparatus

Modern Variety

There is a staggering amount of digital photomicrographic equipment. Modern student or college level microscopes outfitted for photomicrography have moved away from the previous standard of the tri-nocular head with detachable camera, and are now frequently found with dedicated integral digital cameras. The downside of such cameras aside from the added initial expense (which may double the cost of a comparable binocular microscope) is the inability to upgrade to a superior camera as advances are made or funds become available, and the software requirements. The upside is the possession of a tailored optical system that (ostensibly) has been designed with a knowledge of the microscopes optical system.

The contemporary alternative is the digital eyepiece camera or the eyepiece relay adapter. Despite the versatility of such things their occupation of an eyepiece may greatly complicate the normal use of the microscope. Such secondary optics might just as easily result in inferior image quality depending on the optical system of the microscope. Various artifacts and aberrations may be unavoidable and not immediately apparent.

Classic Variety

Putting aside the issue of format for a moment, classic photomicrographic equipment falls into the same two broad categories as modern digital photomicrographic gear. The traditional attachment camera was designed for use with monocular microscopes and many binocular microscopes were available with an interchangeable monocular body to be used with the photomicrographic outfit. Such apparatus was generally designed so as to use an ocular which could be varied depending on the objectives employed or magnification desired. Unlike modern equivalents most used a beam splitter to provide a viewing port for focusing, those which did not made use of a ground glass screen which could be interchanged with the film or plate holder.

The second category relied upon specialized microscope viewing heads which were designed with a beam splitter which would send a portion of the light into a photomicrographic camera system. Nearly all lines of microscopes by the major houses were available with photomicrographic heads of different sorts encompassing the solely photomicrographic (without provision for visual use) to the monocular and binocular photomicrographic (trinocular). Such microscopes relied on the use of compatible photomicrographic systems generally provided by the manufacturer.

Hazards

An off-the-shelf microscope equipped for digital photomicrography will undoubtedly function but one risks being tied to an overly simplistic microscope that does not meet the requirements of the microscopist as they grow in their ability. The same might be said of a modern or classic microscope outfitted with a digital camera and an eyepiece adapter, with the added difficulty of uncertainty of the suitability of the system. For modern photomicrographic equipment then the chief hazards is inferior equipment and the easy of excessive digital image modification.

Classic photomicrographic gear is only very infrequently available as a complete system in good working order. Obtaining results that do it justice is often heavily reliant on the ability of the user to locate and properly employ gear which was originally designed for use with a given microscope line. Such efforts are often complicated by the lack of relevant documentation or informed sellers§ who greatly increase the difficulty of locating equipment by selling it under some other designation. Recognizing compatible equipment on sight is inherently difficult. Attachment cameras using chemical photographic formats provide resolution that well exceeds consumer grade digital cameras, but one suffers for the time and expense of development and processing of significant numbers of test photomicrographs while getting the equipment in working order.

Recommendations

One can obtain a perfectly suitable modern microscope and outfit it for digital photomicrography at a reasonable cost, assuming of course the images are not required to be used for serious work. A student microscope designed for entry level photomicrography might easily run $500.00 US and one suitable for college level work could exceed $1000.00 without batting an eye. Regrettably, such microscopes are generally inferior to used professional microscopes of similar cost, but for assurance of capacity one could not be faulted for going that route.

A used professional grade trinocular microscope (such as the B&L DynaZoom, DynOptic, BalPlan, AO Spencer 10, Microstar, or 2/4) from any of the major houses may generally be found for far less than all but the cheapest modern student microscopes. Many microscopists have no interest in chemical photomicrography, however, what is seldom considered is that such microscopes as mentioned above existed at a time when the C-mount video camera was in wide use. After obtaining a trinocular microscope one should endeavor to find the c-mount photo-tube sold by the original manufacturer. This author is personally aware that such tubes exist for Bausch & Lomb and AO Spencer, an is told it is true of Olympus, Ziess, and Nikon as well.

One may just as well go the above route and in place of a difficult to find c-mount tube purchase a widely available Polaroid instant camera system designed for the microscope. Film remains available for the more common formats and one has all the benefits of chemical photography without the need of expensive darkrooms or tedious developing processes.

Notes:

∗As distinct from antique photomicrographic equipment which should be taken to include the bellows outfitted horizontal and vertical cameras.

†Alternatively the microscope head might be equipped with a control which would direct 100% of available light to either the ocular(s) or the photomicrographic outfit.

‡By this is meant the difficulty of using a system that can not be tested before hand—most equipment must be purchased on the internet—and the difficulty of recognizing unforgivable visual artifacts and aberrations as a beginner.

§Most of the authors photomicrographic equipment was obtained from dealers who incorrectly identified it as projection or aerial photography gear.

Saving Slides With Mountant Issues: III

The Process Thus Far

A quantity of well stained serial sections was obtained for nearly nothing. The slides so far have suffered greatly, some catastrophe reducing their original mountant to a crackling obscure matrix secured under a cover glass yet utterly unsuited for microscopy. Softened by a period in turpentine the fouled mountant was dissolved enough for the original cover to be stripped from the preparation. Thus exposed, the remaining mountant was washed from the sections with further turpentine. Now an essentially new specimen has only to be mounted.

Considerations

Serial sections are laid out according to various conventions and generally in a way so as to fit beneath covers of any of a half dozen readily available sizes. When the original covers were removed they might have easily been retained and reused after a thorough cleaning. In this instance the cover slips were simply placed into a jar with all manner of other cover slips which are being retained until such time as the author forgets about them or gets around to cleaning them. If the sizes were uncommon or otherwise not available it would have been a different manner. Any cover glass removed that was observed to be in any way damaged during removal should of course not be used for mounting again.

When selecting new cover slips one should consider size above all else; size matters. Size of course referring not only to the dimensional area of the cover slip but to the thickness (or gauge number) as well. One should select a cover slip so as to protect as much of the specimen as possible without covering an excessive amount of empty space and having a thickness corresponding to that for which the objectives likely to be used are corrected. Nearly every slip required a #2 cover slip measuring 24mm by 50mm.

Working with large cover slips can be a great challenge. The large size renders them more easily broken in measuring, cleaning, and general handling. One need only break a couple to get the necessary feel for it. Fragility aside, if they are not often used one will have a considerably harder time at applying a sufficient but not excessive amount of mountant than one will have when using a more familiar size. If too much mountant is applied one will find that air bubbles will more easily get in. In part this may be overcome by using a more viscus mountant and applying it over a thin film of solvent on the surface of the specimen.

One must also select a mountant which is suited to the specimen. Stained sections prepared in a laboratory setting often make use of a mountant which is convenient rather than one which is permanent. Convenience may mean the mountant is rapidly cured or particularly well suited for showing the structures looked for. Before selecting a mountant ensure that the solvent used in removing the previous mountant is miscible in that which one would choose. If it is not one will need to get the slips into that solvent by degrees to avoid damage to the specimen and ensure proper penetration. Turpentine being miscible in balsam meant that this tried and true mountant was a logical choice.

Mounting

The process for mounting the reclaimed slip anew is precisely that used for any mount. Ensuring that the specimen does not dry out, but is not flooded with excess clearer, place it on a low temperature warming table, or draw it over (but not through) a burner to warm it. Place then upon the slip a quantity of mountant and permit it to rest somewhat, allowing the mountant time to spread out but always ensuring that the specimen is not permitted to dry out. After a minute or so use a cover glass forceps to place a well cleaned cover glass upon the surface of the mountant. If just the right amount of mountant was used one may count on the cover glass alone for weight and may set the slide aside or into a cool oven to cure.

In general practice one may be sure that too much mountant was applied. This eventuality requires that steps be taken to ensure that the cover glass lays securely in place and is uniformly flat. If steps are not taken one may find that one side of the cover is significantly higher than the other. Place the slide into a cool oven or upon a warming table and permit it to stand for an hour. After this time one may be reasonably sure that the mountant is marginally more dense but still quite fluid. Place upon the center of the cover a small weight corresponding to the shape of the cover and return it to the warming table or oven. After a quarter hour check upon the slide to ensure that the cover slip has not displaced. If it has far too much mountant was used, or the oven (or warming table) is not level, and one will need to slowly but smoothly reposition the cover.

When the slide has cured it is a simple matter to clean any exuded mountant.

Results

In part I of this series we saw a representative example of one of the damaged slides, so badly degraded as to be entirely useless for microscopy. Permit then a look at it now, and yes it is indeed the same slide; note the engraved number.

This slide might look familiar.

This slide might look familiar.

A quick look with the microscope shows that in spite of the severity of the damage shown in the old mountant, the specimen came out unscathed. Any small particles of the old mountant which were not removed will be immediately apparent but one might always repeat the process if one was not scrupulous in their cleaning.

At low power (10x Plan-Achro objective) with the BalPlan.

At low power (10x Plan-Achro objective) with the BalPlan.

High-dry (43x Plan-Achro objective) with the BalPlan.

High-dry (43x Plan-Achro objective) with the BalPlan.

Notes:

∗Correction collars and draw tubes not withstanding most manufactures correct for a particular cover glass thickness across their entire line, in perpetuity. Bausch & Lomb has corrected their objectives for .18mm (#2 gauge) from the first and (considering that a variation of as little as .03mm in thickness will require an adjustment of the draw tube of 30mm) one would do well to gauge their cover slips before use.

†It is my considered opinion that in no case is it better to use too little mountant, err on the side of caution but do not drive to excess.

Once again an excessively long post, sorry for that. Next time I’ll try something shorter, I swear! -K

Saving Slides With Mountant Issues: II

Correcting the Damage

After determining that the slide is a good candidate for rehabilitation one must remove the the degraded mountant and the cover glass. Doing so is not a difficult or tedious task but it will require a degree of patience.

Removing the Cover

The first step is to determine a solvent that will dissolve the mountant without unduly harming the specimen. Working with the knowledge that most mountants which discolor to yellow in areas where it has been exposed to the air contain a natural resin, one finds a starting point to identify a suitable solvent. In many cases a comparatively gentle solvent such as the pure gum spirit of turpentine will prove satisfactory. Whatever the mountant and solvent, placing a drop of solvent on an area where the mountant extends beyond the cover slip is the simplest means of determining its suitability. After a few minutes the heretofore brittle mountant will take on a sticky, thick syrup consistency if the solvent is able to dissolve the mountant.

For some synthetic mountants one may find alcohol works well, however, the frequent use of alcohol as a destain in the initial slide preparation may lead to the loss of vibrancy in the specimen. Other options of more rapid action (but more pronounced hazard) may be benzine, xylene, dichloroethane, or chloroform. On the opposite end of the spectrum in cases where more gentle action or greater safety is desired one may employ various essential oils such as the classic, clove oil.

Once a solvent is identified one need only place the damaged slide into a suitable vessel filled with an ample quantity of solvent. If many slides are to be rehabilitated one may choose to employ a large staining vessel and rack. If only a few must be processed a small Coplin staining jar or in a pinch a slide mailer may be used. One should keep in mind that as the solvent acts upon the mountant its strength will be depleted and the time required will be greater.

From left, vertical Coplin, plastic slide mailer, horizontal Coplin.

From left, vertical Coplin, plastic slide mailer, horizontal Coplin.

Above may be seen a few suitable vessels. The plastic slide mailer is useful only for the less volatile solvents and is recommended for no more than one or two slides. The vertical Coplin jar has a volume more than double that of the slide mailer and is well suited for from two to four slides. The horizontal Coplin jar has slots for ten slides but the most that can be recommended is eight. One may of course load each vessel to capacity if one is willing to permit the dilution of the solvent to such an extent that the process will take a week or more.

After a period of from 24 to 72 hours one may expect the mountant to be largely dissolved. At this time one may remove the cover glasses. Occasionally the condition of the mountant upon removal from the solvent will be such that the cover will have come off without the need for additional effort. If a cover glass should remain in place one will need to raise it by carefully inserting a needle or blade under one edge. Once accomplished, surface tension should be overcome and the cover easily removed. If the cover is seen to flex significantly one must forgo removal for the time being. A cover glass support (or more economically a portion of a broken cover glass) should be inserted just enough to maintain a slight lift on one side of the cover glass and the whole then returned to to the solvent.

Provided the slides were well prepared initially and the solvent selected was not undually harsh there should be no risk of sections coming away from the slide or adhering to the cover.

Removing the Mountant

With the cover removed one should take care not to permit the surface of the sections to dry. There is liable to remain a significant quantity of partially dissolved mountant on the slip. To remove this, one will require additional solvent. Resist the urge to employ the same solvent that was used previously; it has been rendered too weak and will now contain all manner or particulate contaminants. Depending on the time one has available one may proceed with one of two methods described below.

The fast method requires a slide clamp, a circle of filter paper, a funnel, a ring stand, a beaker, and a pipette. Pour a quantity of solvent into the beaker and placing the filter paper in the funnel position it in the ring stand over the beaker. Grasp the slide with the clamp and holding it in one hand over the mouth of the funnel use the pipette to send a gentle stream of solvent over the slip so that any particulate matter that washes off is caught on the filter paper. Refill the pipette from the beaker and repeat until the slip appears free of undissolved mountant. This method is particularly well suited for use with more profoundly damaged slides or particularly delicate specimens as it affords a degree of fine control and permits the technician to immediately notice any detriment to the specimen.

The fast method. At the bottom of the frame may be seen a watch glass holding a quantity of removed cover glasses.

The fast method. At the bottom of the frame may be seen a watch glass holding a quantity of removed cover glasses.

The slow method is simply a continuation of the previous process. One should use a new vessel and again additional solvent. If one is forced to use the same vessel one must be sure it has been scrupulously cleaned. Take care that all slips are arranged so that any particulate mater dislodged from one slip will not fall upon another. In practice this means that wherever possible slips should be positioned back to back. After a period of three to twelve hours all the solvent should be removed. Rinse the slip then with a pipette of fresh solvent to ensure no particulate contaminants are present on the surface. This method should not be used with powerful or excessively volatile solvents. It is also unsuitable for deeply or contrast stained specimens.

The next post will treat with re-remounting the slip. If you’re not used to working with large cover slips you’re in for a treat! -K

Notes:

∗For some subjects it was accepted practice to adhere sections to the cover glass rather than the slide. This is exceedingly uncommon in preparations younger than 80 years or so. Thicker sections are sometimes attached to the cover but such preparations were likely made by students in an effort to salvage an otherwise unusable section, so be cautious with slides that have the signature or a novice. There are methods for handling such slides but that would make a long post longer.

†Of course one could go right ahead and completely destain the specimen. Followed to the extreme this method would provide one with what is in essence a newly prepared slip ready for staining. Again though, I am trying (and failing) to keep this short.

Saving Slides With Mountant Issues: I

Obtaining Damaged Slides

Very often the amateur may come upon the opportunity to obtain significant quantities of prepared slides of a type that makes use of methods or materials that are not generally within the scope of ones own activities. Such slides may provide valuable objects for study. Regrettably, one may find that many slides prepared in professional circumstances only find their way onto the market at excessive cost or when damage sustained in one way or another has rendered them unsuitable for study.

Recently a quantity of slides were obtained by the author that consisted of serial sections from Leptonycteris sp. The exceptionally thin and expertly stained sections were mounted in series under rectangular 18x40mm or 24x50mm coverslips. All of the slides showed degradation of the mountant to a greater or lesser degree characteristic of repeated stress from heating and cooling.

Due to the visible damage 75 individual slides were had for the incredible price of ten United States dollars. One would be hard pressed to obtain a similar number of blank slips or coverslips for the same price.

Assessing the Damage

Visibly degraded mountant, black background.

Initial observation showed that the slip was in fine condition without chips or cracks which would greatly complicate the task of rehabilitation. Despite the significant degradation of the mountant the cover slip remained firmly in place, a good sign that the sections beneath would be intact. Running a fingernail over the cover is often all that is required to determine if the coverglass itself is similarly undamaged.

Visual inspection showed the mountant to be significantly degraded on most of the slides. Pronounced yellowing at the edges gave way to white patterns where mechanical damage had caused the mountant to crack to an extent that it was no longer in optical contact with the coverslip. In some instances the mountant had become brittle to the point that the coverslip had come off entirely. The areas occupied by the specimen were invariably damaged even in places where the surrounding mountant remained sound, as may be seen at the extreme right of the image at left.

Under the microscope one could observe the extensive cracking of the mountant shown below. Focusing on the specimen with a 16mm objective was nearly impossible as the depth of focus afforded by the objective ensured that the cracked mountant would intrude into the image plane. At higher levels of magnification one could optically section the image enough that the cracks were not immediately evident, but resolution was impaired to the point of near total occlusion of any detail.

Photomicrograph showing degraded mountant.

Photomicrograph showing degraded mountant.

Projection Microscopy III

The Set Up

The 1 Inch is old enough to be corrected for a 10 inch tube length so when setting up for micro-projection one must be sure of two things; first, that if an eyepiece is used that the draw tube is able to provide for that distance, and second, that the projection distance is measured from a point 10 inches beyond the rear lens of the objective if an eyepiece is not used. For simplicity a dedicated projection microscope will be used for testing. It is a Bausch & Lomb dating to 1956 and was intended for use with its own projection objectives (distinct for the orientation of the B&L logo on the objective barrel). The intensely bright lamp integral to the stand will have no difficulty providing adequate light.

According to published information from the manufacturer contemporary to The 1 Inch, one knows that a minimum projection distance of 15 feet is recommended for the most highly corrected image. A projection surface (in this instance a handy, blank, artists canvas) was positioned 16 feet from the stage of the projection microscope. With the head of the microscope properly aligned a projection distance of just over 15 feet was obtained.

Results

It’s would appear that obtaining a digital photograph of a projected image is not a job to be entered into lightly or in haste. Apologies then, but please understand that in person the image produced by the objective is in a word: astounding.

Stained section of human skin

Stained section of human skin.

Palp of wolf spider mounted whole with pressure.

Palp of wolf spider mounted whole with pressure.

The low light conditions and poor handling of the same by the author and his 14 year old digital camera do such little justice I considered not including the images at all. For several hours (until other responsibilities intruded) various specimens demanded projection and rapt attention. During this time there was no noticeable heating of the objective despite the intense heat of the lamp. In fact having previously made use of the objectives provided with the stand I can say that The 1 Inch remains cooler than those of much more modern construction.

Color correction is as better than that provided by any objective alone that I have seen. In spite of the long projection distance flatness of field was observed to be quite profound. Using a wall as the projection surface, images spanning 5 feet were observed to be in nearly uniform focus across their entire diameter.

I will have to read up on low-light photography in the hopes of sharing more accurate portrayals of the abilities of The 1 Inch. -K

Projection Microscopy II

An antique B&L projection objective of 1 Inch focus

An antique B&L projection objective of 1 Inch focus

An Old Objective

The above is a Bausch & Lomb objective (hereafter dubbed The 1 Inch) of indefinite age. It is shown with its canister and marked as follows: “Bausch & Lomb Optical Co.” in the old style gothic lettering, “ROCHESTER, N.Y.” in uniform san-serif block upper-case capitals, “Projection” in large first letter upper case serif capitals, and finally designated “1 In.” in the same style beneath that. One acquainted with the Bausch & Lomb line will immediately recognize it as dating to before the 1930 catalogue, when objectives were listed by power and equivalent focus in millimeters. That the focus is marked in inches one will quickly note places it at least in the era of the 1899 “Catalogue A” except that at this time the objectives were marked also with the tube length. It is likely then that the objective is older than 1899, and that being the case, further likely that the tube length is the traditional long form (10 inches or 250mm) rather than the short (160mm) to which one will be accustomed. Thankfully, the objective is to be used for projection and dates to a period when oculars were not required (though could be employed) for projection or photomicrography.

Taken as it stands with only the marked information known one can take 10x for the magnifying power of the objective. It was simple in the days of the ten inch tube length to calculate the power of an objective from its imperial focus integer be that whole or fractional; a ten inch tube length is divided into marked focus of the objective providing a designation of magnifying power. To anyone accustomed to shorter tube length objectives The 1 Inch will seem of unusual size for a low power. A certain amount of this attributable to the longer tube length for which it was corrected, though most is due to its mechanical construction as dictated by its use.

Its Build

The 1 Inch is housed in a traditional brass RMS threaded body, but one will note immediately the oddness of its front element. Robustly constructed of black metal without a finish, the component is less an optical element and more a shield. It may be unscrewed to reveal a recessed front lens which is nearly twice the size of the aperture in the shield. Further investigation shows that the front and rear lenses of the objective are separated by a considerable distance. The combination nearest the eye (the rear, or posterior, element) is definitely composed of multiple lenses.

Note the large size of the anterior optical element.

Note the large size of the anterior optical element.

That the shield serves as both an aperture and heat shield so that the heat generated by the intense light required for projection does not damage the optical elements of the objective seems obvious. One may also feel assured that the large diameter of the lens elements owes to the need for the objective to provide a very bright image. For a 10x objective of such advanced age to be composed of quite so many lenses at first seems strange until one considers the need for the objective to provide an unusually flat field of view without any assistance from intermediate lenses or compensating oculars.

Its Use

In its day the objective likely was used with combustion lamps. Intense sources such as the limelight or Wellsbach gas mantle may have been employed when projection was required over any significant distance. For photography or short projection it may have been possible to use a well-condensed oil lamp or cut window shade so as to permit the use of daylight in an otherwise darkened room. The objective may have continued to see service after the commercialization and wide availability of electricity brought such options as the carbon arc lamp and incandescent flood into use, but one may only speculate.

The use to which The 1 Inch was put is well known, that use of course being projection. Consulting an early edition of Bausch’s Manipulation of the Microscope provides that a projection objective should be used at a projection distance of 15 or more feet. Gage, Carpenter, and other authorities, recommend projection objectives for micrography either alone or with suitable oculars. One may be assured that except in extraordinary circumstances no one was making micrographs enlarged to the extent had at a 15 foot distance, so that the use of the objective for smaller projections is suitable.

However it was employed, one may be certain that The 1 Inch saw a significant amount of use. Projection was practiced rather more often in the early days of microscopy and for some the method was so frequently called upon that it was not adequate to merely rely on a simple achromat. Throwing an image upon a screen across the room was, and remains, no mean feat for any (excuse the insult) humble microscope.

∗Likely, but by no means certain. Methods exist for determining the optical and mechanical tube length of an objective for which these are not known, at some later date these will be treated with.

†For details on the calculation of power from equivalent focus please see my earlier entry on the matter available here. The link opens in a new tab or window.

Next time: The 1 Inch in action! -K