Ringing a Slide: Practice

I accept full responsibility for the following as the majority is not attributable to any particular authority but only my own experiences. -K

In practice ringing a slide (this deals only with circular covers, when treating with rectilinear covers I will refer to it as sealing) is a simple task and once performed is easily repeated indefinitely, provided a few points are always observed. The keys to successful ringing are entirely mechanical and essentially every other aspect can be overlooked provided the mechanics are given priority. For example the sealing cement is less important than it’s viscosity and the position of the ring much more crucial than its appearance.

The easiest cement is often the one on hand, but for beginners or those wishing only to get a feel for the practice I can not more highly recommend gold sizing. For those unfamiliar, gold sizing is a gilders sizing cement for the application of (primarily) gold leaf. Any of the larger art supply houses can provide a suitable gold sizing and it may generally be found among the model paints. Available in a number of grades, look for one which is described on the label as “fast drying” or “suitable for exterior varnish.” It will likely be the least expensive of the sorts on offer. Do not purchase gold size which is described as “for picture varnish.” Higher grades of gold sizing dry incredibly slow, some behaving more like an oil paint in that they never set up completely which is wonderful protecting art which needs to breath, but not for sealing a coverslip.

Acquire also a fine camels hair brush, any will do provided it may be pointed (either purchase a pointed brush or plan on trimming it) and has natural bristles. Gold sizing may be cleaned from the brush with xylene (xylol in Germany and many continental European countries) and many synthetic bristles will dissolve partially (or completely) in xylene and similar solvents (benzene &ct.).

One should already have a ringing table of some sort. If not, Brunnel in the UK and BioQuip in the US appear to be the only contemporary sources. If one would purchase a second hand turntable or construct one for themselves it must be outfitted so that it turns perfectly without wobble, and freely completes many revolutions at a fair speed without slowing. There should be a simple means of holding the slide quite firmly and some convenient and sturdy rest for the wrist and forearm. I prefer a rest which supports the hand above the surface of the turntable so that the wrist may be held straight while holding the brush vertically over the slide.

Prior to beginning one should clean the slide thoroughly; first scraping any exuded mountant with the dull side of a heated scalpel and following by a lens paper wet with a small amount of an appropriate solvent. When positioning the slide to be sealed upon the turntable one must be sure to center not the specimen, but the coverslip. With turntables that are marked by concentric rings (as most are) it is simple to get the position if the coverslip is near to the size of a marking. In any case once believed to be centered set the turntable spinning and look down from above to determine that it is indeed centered. A ring which is not concentric with the edges of the cover will serve but is less secure and less effective.

Effective position seen at right.

Effective position seen at right.

As seen in the right half of the above image holding the wrist straight helps to maintain a steady hand and places the point of motion at the more sturdy joint of the shoulder rather than at the wrist. It’s rather similar to the form one uses when writing in the Palmer method, for any old enough to remember being instructed in that technique.

Why though should it matter if the hand is kept steady? The seal is applied in an instant by just touching the tip of the loaded brush to the slide, and as the turntable should be rotating a fair clip it only requires a second or two for the ring to be built up by many revolutions. In that short time there is little opportunity for motion to be sure, but the place at which the ring is applied is paramount and ensuring a minimum of motion keeps the ring from being located improperly.

The author is of the oppinion that an improperly positioned ring is worse than no ring at all. Being improperly positioned a ring fails to adequately seal the slide and presents significant chance for damage when it must be removed either to remount the spoiled specimen or to properly ring the slide in the future. For preservation, the ring should be applied so that it’s thickest portion is adjacent to the corner created by the bottom of the coverslip and the top of the slip. Covers which have been first properly sealed may then be added to with decorative and functional pigments which extend farther onto the other surfaces of the coverslip or slip. Concentric rings of contrasting colors may be laid down with ease that present an eye-catching and very finished appearance, as long as their is an underlying ring located correctly such additional layers can not but help, however superfluous they may be.

Note the outline at the top right

Note the outline at the top right

Taking a sidelong glance at a cutaway provides an illustration of properly positioned rings. On the top are rings which are excellent; just covering a portion of the coverslip and slide and presenting a significant barrier to oxygen infiltration or volatile compound escape. The example at the upper-left is representative of the sort of seal one is likely to find on antiquarian slides and is achieved by successive layers of cement or the use of a highly viscous cement. Asphalt varnishes or gum/rubber bearing shellacs will produce a ring of this character in a single application. The image at the upper-right is what one can expect of a properly located ring of gold size.

Below are rings which although correctly located will provide almost no protection. On the left one can see the product a ring which suffered for either being applied with too much pressure on the brush (just the faintest touch is needed) or with a cement of to low a viscosity, the thin cement spreading out because it was not substantial enough to support itself in the place of the force created by the spinning turntable. At the right one sees the cut-away of a ring that was applied without flowing freely from the brush. If the cement will not flow properly onto the slide one might need to first wet the brush in a small amount of the solvent to encourage a healthy flow. Another cause of rings of this sort is an unclean slide, which can result in rings that flow excessively or are seemingly repelled by the surface of the slide (depending on the nature of the contamination).

At some later time I will try to post some of the very serviceable sealing cements I have employed over the years and speak to the virtues and vices of each. For the time being I recommend those who desire an excellent all-around sealing cement stick with gold size as it is perfectly serviceable for most needs and of high quality. I must say that many cements available, at first seemingly excellent are much less impervious to the compounds apt to find their way onto a slide as it is used. Simply being available from a reputable supply house is not a proof of serviceability and one should never rely on an untested cement for a valuable preparation.

Ringing a Slide: Theory

I think it’s a great pity the commercial houses do not anymore seal slides in a fine varnish, but that’s just me. -K

Ringing a slide, just as often to be referred to as sealing a slide, was once a ubiquitous practice among not only amateur mounters but nearly all microscopists. The motivation for sealing a slide with any cover was preservation. Of course some permanent mounts were not required to last indefinitely and were not commonly ringed, but for some time seemingly every slide which bore a cover was sealed in some manner. Circular covers were ringed. Rectilinear covers were likely to be sealed as well but the methods were more apt to include waxes and methods that were less well known.

If one has had the opportunity to examine slides of significant age, particularly those that were never sealed, one may have noticed that the mountant is no longer the water-clear of a fresh balsam mount. All balsam will exhibit some tendency to darken over time, some more than others. Balsams that have had their volatile oils driven off and replaced with an alternative solvent may yellow more or less depending on that solvent; Benzene more than, Xylene and Xylene in turn more than turpentine. Other factors are at play as well such as the clearer used or the perfectness of the specimens dehydration. Some more simple factors may be at play as well, for example more acidic balsam tends to oxidize to a greater extent than so called neutral-balsam mounts.

Which brings us to the root of all the yellowing: oxidization. The infiltration of oxygen is the cause of yellowing in many mounts, be they damar, balsam or what have you. This is why then one observes yellowing in a mount it invariably encroaches from the edges of an in-tact cover (or an air bubble) and is more pronounced on the limits of the cover. To prevent the encroach of oxygen and retain the refractive index of the mountant it is necessary to seal the cover. Wax, goldsize, varnish, enamel, even rubber and gold leaf have been employed to seal the borders of coverslips with more or less success.

As a mountant cures the volatile components escape from the edges and the mountant solidifies. Initially the solidification of the mountant at the edges results in a coverslip which seems solidly bound to the slip. If an inattentive microscopists should accidentally rack down an objective too far and crash into and break the coverslip of a slide, the microscopist may be surprised to find that the mountant remains somewhat liquid deep within the mount, even years post preparation. The mountant will not generally begin to yellow as a result of oxygen infiltration until such time as the volatile compounds are exhausted. With many mountants the last of those volatile compounds will not be driven off until long after the mountant is solid.

This is the reason one may have heard that rapidly cured slides are more brittle than slides which are allowed to cure slowly at low temperature. A slide cured rapidly at high temperature is able to exude more completely its volatile components because although it must still escape from the edges of the cover those edges remain more fluid (gas permeable) due to the heat applied. For a quick demonstration one may place a drop of balsam uncovered on one end of a slip and a second covered with a coverslip on the other end of the slide. If this slide is left for several hours on a low temperature hotplate one will notice the uncovered drop (which should flatten nicely) is noticably yellowed and the balsam beneath the coverslip remains quite clear.

When sealed the mountant is prevented from venting it’s last remaining volatile components and retains it’s original appearance for far longer. The substances used to seal a coverslip are effective because they are not covered by a coverslip and so very quickly solidify and create a barrier to oxygen and the escape of the remaining volatile components of the mountant. For this reason sealants which are composed of substances very similar, even thinned with the same solvent as the mountant, may still provide acceptable results.

Some mountants (Euparal for instance) will not oxidize over time and do not need to be sealed to preserve their original appearance. The sealing of mounts may also be done for aesthetic reasons only. Layers of sealant in contrasting colors may be built up around the borders of a cover to great effect and a simple black ring may often prevent the inattentive from placing an unlabled slide upside-down upon a stage. In the end, sealing a slide may be a matter of superficial preference or a means of ensuring ones slides endure in superior condition for future generations. In the next installment we’ll take a practical look at slide ringing.

Slide Catalogs, Indices, and Labels II

Time for another exciting bit of truly important tedium! -K

Part Two; Catalog and Index
From the previous post it should be clear that the form of label can vary wildly as can the information on it. Its hardly possible to fit all of the useful information one might have concerning a specimen, or its treatment, on a slides labels. Logically the thing to do is place the more extensive information in a secondary location where it is both accessible and organized: a catalog or database of some kind is warranted.

The information kept may be standardized across an entire collection or it may vary and be tailored to each slide depending on what is relevant or known. The decision on whether to maintain a constant or variable set of information is as much a mater of preference as the choice of what to include on the slides label. Information may be spartan and limited only to that which not obvious, or robust in the extreme filling an entire sheet of paper.

This raises an other question, the choice of medium on which to compose the catalog. One can compose the catalog on traditional media such as looseleaf paper kept in a binder, or a series of index cards in a file. The variety of digital options is quite extensive, specialized software will prove popular with some while a simple spreadsheet or web based database might be preferable for some hobbyists. For particularly large or complex collections a digital catalog can prove expedient if for no other reason than its being rapidly searchable and previous entries are more easily updated or expanded. A hard copy catalog of printed forms filled in by hand with ink is often simpler to use in practice.

Papers recommending the form which a slide catalog can take and the information one should include date to the nineteenth century and may be found in any number of texts. Guides on the subject are not infrequently written for slides produced for a particular study or by a specific laboratory; what is required of a catalog for one series of slides may differ substantially from an other. Few recommendations exist concerning the catalog kept by an amateur and such a catalog faces all the challenges of a curators catalog and more.

Specimens may be of enormously different sorts and of massively divergent ages. The knowledge the cataloger posses of each slide may be likewise variable. If one relies on a catalog where the information recored is constant regardless of slide, there is a substantial risk that many fields will necessarily be left black for slides which are purchased as opposed to slides which are prepared by ones self or vice versa. One may side step such a pitfall by using only broad information in ones catalog and providing a section where particular notes unique to each slide may be entered.

An index of some sort if useful simply for providing ready access to the information of a desired slide, or type of slide. With a digital catalog a traditional index is largely superfluous as the rapid searching provided by the software used should negate the need for a formal index. For a paper catalog one may organize the index around a handful of useful information, such as the specimens name, or the type of preparation. It is a simple manner to adapt a printed address book and make entries alphabetically which correspond to numbers in the catalog proper or pages of the catalog. One may also use the index to locate slides if entries within it point to the location where the slide is stored. If at first such an index seems more labor than it is worth when a substantial number of slides are had it will prove useful, particularly for the aid of collections that are used by others than the curator.

Whatever manner of catalog is kept, in whatever form, it is undeniably of great utility particularly when one begins preparing or collecting permanent mounts. If one simply tucks slides into cases as they are acquired it will become all to easy to lose track of a delightful preparation just when it is most needed. A catalog serves to fix a means of organization as much as a method of retaining information that will not fit upon a slides label. I have no wish or standing to set a best program for the creation of a slide catalog but as with labels I will attempt some broad standards that will help inspire one who wishes to compose a useful catalog.

  • Each entry should bear a number that corresponds to an indelible mark on the slide to which it corresponds.
  • Each entry should inform upon the location of the slide in storage, i.e. Box A, Slot 1 etc.
  • Each entry should inform upon the provenance of the slide.
  • Each entry should identify the preparation by the name that is marked on the label of the slide to which it corresponds.
  • Each entry should include both the common name of the specimen and its scientific name if known.
  • Each entry should identify the source of the specimen; point of collection if known, limited to type if unknown i.e. whole mount, transverse section, smear etc.
  • Each entry should describe in general terms the process used in preparation if known.
  • Each entry should include the mountant used.
  • Each entry should include the date of mounting if known, the date of acquisition is unknown.
  • Each entry should inform as to the gauge of coverslip used.
  • Each entry should include a section for notes of interest not provided for elsewhere in the catalog.

Next post will be about mounting a specimen or two, I promise!

Slide Catalogs, Indices, and Labels

When building up a collection of slides it’s not uncommon for the collector to simply put them up in a case without a thought to organization or logging. It’s too bad considering the tools available to keeping track of things. Labels are an old tool but still of value. -K

Part One; Labels

I’m old enough to remember with apprehension the advent of digital catalog systems. I remember when looking for “that article about you know, the new study” in a journal whos name wasn’t remembered meant hoping the librarian knew your field at best, and wading through a cross index compiled by some other librarian at some other library and hoping a name seemed familiar at worst. Digital cataloging and inexpensive terminals changed all that. It became possible to dispense with a wall of tiny drawers and an army of clerks pounding away at typewriters loaded with cream colored cards. Keeping records became faster with the digital revolution, at least as far as looking things up went.

Putting records into the system, whatever system, is still time consuming. In place of typewriters there are keyboards and in place of cards there are fields on a database program. Of course keeping records can be faster now but it still requires some time and thought. What has any of this to do with microscopy? Slides of course. The cataloging used in libraries is rather similar to that needed for keeping slides organized so it’s only fitting that the two might be compared. Books however, have a bit of a leg up on the average microscope slide; there are pages within a book dedicated to identifying it. Slides have their labels, ideally, but often they are nearly useless for the sake of brevity.


Oh AmScope what horror is next?

The record keeping associated with the utility of a microscope slide is often overlooked. It’s tragic that the modern supply houses putting out their cookie-cutter slides, however well made and nicely stained, tend to put next to nothing on their labels. The nearest thing to a catalog is usually a printed card with only the name of the specimen and maybe a number corresponding to a slot in the case. One can see an example of this sort of modern prepared collection above. It is simple, mass produced, dubious in quality (notice specimen 2, Coprimus? because of course they can’t expect an underpaid technician to know that Coprinus is a genus and Coprimus is gibberish) but inexpensive and readily available.

When purchasing antique slides the collectors knowledge of the mounter or the uniqueness of the specimen, even the artistry of the preparation makes up for the usual absence of any extra notes. It’s noteworthy though to consider the differences in the labels on a modern slide and one of significant age. Below are two slides, each from a recognizable firm but of significantly different age. The primary market of each company varied as well. The more contemporary company markets almost entirely to young students and their teachers, the older served professionals, and amateur enthusiasts of every age.


One of these things…

On the more modern slide the information provided is rather limited to say the least. It is labeled “Bacteria Types w.m. Ba 020 Carolina Biological Supply Company”. Certainly knowing it is a slide of whole mount (w.m.) bacteria would permit one to look in the right text for identification but there is plenty of space on the label so it wouldn’t have been impossible to put the type of bacteria on the slide itself. Knowing the company and seeing their own catalog reference (Ba 020) would make it a bit easier to track down more information about the specimen but not knowing a date and considering the recent changes at Carolina finding out anything further about the slide will be difficult. As an example of different bacteria types the slide is useful, but as a representative specimen it is quite useless without a good deal of effort.

The older slide is from W. Watson & Sons and also has rather limited information on it’s labels. However, the quality of that information is entirely more useful because the mounter knew the intended use of the slide. The slide is a test slide, made of a known object under rather exacting conditions so that it may be used to test the quality of a particular objective. One can see that the specimen is of Pleurosigma angulatum and that it is mounted in Styrax. Knowing the mountant is necessary for test objects (or any specimen) because without it (or more specifically the refractive index of it) one can not measure the thickness of the specimen accurately. Electron microscopy has largely eliminated the arguments concerning the actually form of a spring-tails scale but an objectives ability to resolve one is a classic measure of quality.


…is not like the other.

Above one can see two more slides, of an entirely different sort than the previous two. On the left is a blood smear from a Hematology laboratory while on the right are two serial sections of primate brain from a research laboratory. One has a pasted on label which has a coating of balsam, while the other is marked in ink on its frosted end. One has only cryptic markings that are seemingly useless without a knowledge of the specimen and the logging practices of the lab, the other is clearly marked, immediately recognizable and identifiable without additional information. Neither has any information about the specimen preparation or treatment, neither has a date, neither informs on the mounter or the mountant.

On the slide to the right one can see that a printed label reading “Clarkson Hospital Laboratory” has had “Chronic Lymphatic Leukemia” typewritten on it. One may find that Clarkson Hospital is likely Bishop Clarkson Memorial Hospital once of 415 South 26th St. Omaha Nebraska which closed it’s doors and merged with University Hospital in 1997. From the appearance of the label and by virtue of digging into the history of Clarkson one could date the slide to the 1950’s without to much trouble. The characteristic color of the smear makes it rather simple to guess the stain employed and a hematology text of appropriate vintage might even provide information on the preparation method, but it would only be a guess. A textbook with color photomicrographs would likely replace the function of this slide in a modern hospital but as an example of the condition it depicts it is still useful.

The slide on the left reads only what looks like “511 GABA 1:1000 C8 Elilè”. Cryptic to say the least, but the specimen is clearly a section of brain. From its size and morphology one might easily guess it is of a small animal, likely a primate. Looking about for a connection between the markings on the label and primates one can find reference to gamma-Aminobutyric acid (GABA) receptors in the field of neurophysiology without too much effort. The first number is no doubt a catalog or subject reference, I can only guess at what the ratio might be in reference to but it’s not much of a leap to hypothesize that “C8” is a reference to order of the sections. Being in possession of a second slide labeled the same but for “C9” makes such a guess a near certainty. If I had a subscription to the Journal of Neurophysiology, and sufficient interest, I might be able to identify what the marking in red actually reads or likely indicates. An interesting slide, but even with a more comprehensive label it would remain little more than an interesting object of little utility outside the laboratory where it was produced.

It’s worth noting that the contents of a label change depending on the intended use of a slide as much as they do depending on the time period during which it was produced. Whatever information is placed upon a label is useful, but the use to which that information is put might vary wildly. When one prepares their own slides the only limit on the information on the label is what one imposes for ones self. In the various texts available all sorts of claims are made as to the necessary information a label must have. One can see from the above that this information has never become standardized, nor is it ever likely to become so. Labels then are almost exclusively in the realm of preference, yet permit a few exceedingly general suggestions:

  • One should provide a slide with a label the contents of which are useful to the mounter and the intended audience.
  • One should provide a slide with a label which will endure the conditions of use and storage.
  • One should put their name on each slide they prepare.
  • One should put the date of mounting on each slide.
  • One should include some method of referencing more extensive information than the space on the label permits.

Be sure to tune in next time for more exceedingly boring walls of text dealing only in a cursory way with microscopy!