Volume 12, Number 2, May 1990, pp.9-15

Technical Exchange

Walter Henry, column editor


The Chronicle of Higher Education, Vols 36(12) and 36(15), describe some software that might be of some interest to conservators, especially those responsible for training interns. They are available for $5 per disk:

"Methods of Chemistry: AB 110," for IBM PC series and compatibles, contains a tutorial on significant figures and rounding; a module to print reagent labels and unknown-substance labels on gummed tags for laboratory experiments; and a module which calculates the isotope distribution of an ion.

"Methods of Chemistry: MC 101," for Apple Macintosh, disk has a series of programs for use in physical chemistry, a demo for a Molecular Editor which draws and manipulates molecular structures.

"Chemical Inventory Sorting System," for Apple II series, aids in maintaining an up-to-date inventory of chemicals in a storeroom. Contact:

Department of Chemistry
University of Wisconsin
Madison, Wisconsin 53706

Textile Display

Textile conservators are always looking for things to add to their "bag of "tricks. Over the past decade, there has been a trend towards textile conservation treatments that are passive, non-intrusive and, of course, reversible. The enthusiasm for treatments utilizing adhesives has dwindled and many time-tested sewing techniques have enjoyed a revival. Between 1985 and 1987, pressure mounts, with well-deserved caveats, were the topic of discussion. Now, conservators are comparing notes on the use of slant boards for displaying textiles. It is not a completely new idea; some conservators have been using them for years but recently the concept has been spreading far and wide.

Displaying textiles on a slanted board helps to take some of the stress off the fibers. It is a compromise between the more stressful vertical display and the conservator's favorite for very fragile textiles, horizontal display.

There are a multitude of designs for slant boards, the angle for which has been widely discussed without establishing a standard. Methods for mounting may involve a hook and loop band (such as Velcro) across the top edge, pinning, or placing the textile on a napped fabric. The specific needs of each textile to be displayed must be considered when designing the display mount.

The use of napped or fuzzy fabrics behind a textile artifact on a slant board can be seen in LACMA's exhibition "A Visual Feast: Recent Acquisitions of Costumes and Textiles from the Permanent Collection," open through May 20, 1990. For the textiles selected this display method appears to have been very successful.

There are several napped fabrics suitable for this display technique. One that we have tried is Lynda fabric. This is a 3- ply laminated fabric, containing no adhesive and composed of 100% nylon outer layers with a polyester foam core. Because of the suspected long-term instability of this foam core, the fabric is recommended only for temporary mounts. Lynda is produced by the

J. M. Lynne Company, Inc.
59 Gilpin Avenue
P.O. Box 1010
Smithtown, NY 11788
(800) 645-5044

Velvet loop Velcro fabric, a similar material, is available from Testfabrics, Inc.

P.O. Box 420
200 Blackford Road
Middlesex, NJ 08846
(201) 469-6446

I would like to thank Dale Gluckman for bringing this technique to our attention and Louise Coffey for researching the subject. Louise made contacts with several textile conservators in the United States to learn more about the uses of Lynda fabric, including: Lucy Commoner, Cooper-Hewitt Museum; Lorna Filipine, The Art Institute of Chicago; Jane Hutchins, Museum of Fine Arts, Boston; and Mary Ballard and David Erhardt at CAL, Smithsonian Institution. This is not to indicate an across-the-board endorsement; as with any conservation technique, this one has appropriate and inappropriate applications. There are, most likely, many other uses for slant boards and napped fabrics. We would love to hear about other applications, both good and bad.

Catherine McLean
Conservation Center
Los Angeles County Museum of Art

Serendipitydo? Brij 35 Used Like a Resin Soap

The idea of buffering the pH of a resin soap with triethanolamine and acetic acid to improve its performance was first described to me by Chris Stavroudis last Fall. I began to think that this critical step, which is so useful in controlling the action of the resin soaps, could be useful in the preparation of other aqueous solutions used to clean paintings.

Brij 35, a polyoxyethylene (23) lauryl ether, has been used as an ingredient in a naphtha emulsion (Tween 20, naphtha, water, triethanolamine) formulated by Richard Wolbers. Recently, I prepared an experimental detergent gel using Brij 35 in much the same way a resin soap is made: 2g Brij 35, 100 ml deionized water, 1.5 ml triethanolamine (to increase the pH), acetic acid (to buffer down to pH 8.0, use a 25% stock solution and add dropwise), 0.5 ml Benzyl alcohol, and a small amount of Carbopol 934 stock gel pH 8.0 [see "Solvents and Sensibility, Part III", WAAC Newsletter, May 1989]. I was quite surprised to find that not only did this solution work well to remove the grime, but it was also beginning to solvate the resin coating in much the same way as the resin soaps.

So far, I've found this Brij 35 gel to be quite acceptable for removing natural resin varnish films.

Dean Yoder, Yoder Conservation, Inc.

Painting Conservation Equipment for Sale

Teri Oikawa-Picante announces that painting conservation equipment and supplies will be for sale at her San Francisco studio. For a list, call (415) 621-7005 or write:

102 Buena Vista Terrace
San Francisco, CA 94117

Marble Sculpture Conservation Technique

John Griswold has developed a technique for filling losses in outdoor marble sculpture using Hxtal epoxy, fumed silica, dry pigments and enamelists's glass powder. By combining these materials in varying proportions, a wide range of effects can be achieved. Both the translucent quality of marble and the texture of weathering crusts can be matched. The edge of the loss should be coated with a reversible sealant such as Acryloid B-72 before applying the pigmented epoxy putty. John wishes to thank John Burke of the Oakland Art Museum for his helpful suggestions. For additional details, please call John Griswold at Glenn Wharton's studio: (213) 397-4077 or (805) 565-3639.

Seminar Series

The Conservation Center of the Los Angeles County Museum of Art and the Getty Conservation Institute have jointly hosted a series of seminars on conservation topics at irregular intervals over the past several years. We are now in the process of updating our mailing list. Those who are currently on the mailing list will have received a form by the end of April requesting that they verify their address. This sheet must be returned in order to remain on the list. Anyone who has not received the form, as well as anyone who has been relying on announcements mailed to their colleagues and who wishes to receive their own copies, should send their current address to:

John Twilley
Senior Research Scientist
Los Angeles County Museum of Art
5905 Wilshire Boulevard
Los Angeles, CA 90036.

Temperature and Relative Humidity Measurement

The newsletter of the Association for Library Collections and Technical Services describes the Elan Technical Corporation's HT201 Thermo-Hygrometer, a low-cost, battery operated sensor with a measurement range of 32-166 degrees F and 20-95 percent RH. Priced at $128.85, it weighs 3 ounces and can be wall mounted. Chris Stavroudis writes with considerable enthusiasm about the Model CT485RS High Performance Microprocessor-Based Temperature/Humidity Recorder:

Omega Engineering has developed a computer controlled, electronic sensor temperature / humidity recorder. The 12" x 10" x 2.5", 7 pound instrument records temperature and humidity on a single circular chart. The chart can record 1 day, 7 days, or 32 days (switch selectable) in degrees Celsius or Fahrenheit (also switch selectable). The unit contains batteries (included) which can power the unit for a month. An AC power adapter is included allowing the batteries to function as an automatic backup in case of power failure. The unit is portable or can be wall mounted. Both the temperature and humidity sensors are mounted in a 1/2" diameter, 4" tall metal cage that can either be plugged into the side of the recorder or attached to a six foot long extension cable for remote sensing. Quoting from the manual: "The temperature sensor is a low-power, semiconductor type, with a linear voltage output proportional to temperature. The humidity sensor consists of a bulk polymer material deposited on a ceramic substrate. The mobility of the ions in the polymer changes with moisture content of the surrounding atmosphere." The data from the sensors are fed to the microprocessor controller which makes necessary conversions and updates the servo-driven pen arms. A front panel display shows either the instantaneous humidity, temperature Fahrenheit, or temperature Celsius (switch selectable). The microprocessor also remembers the high and low value for each of the front panel parameters, which is displayed with the push of another button. When the chart paper is changed, the minimum and maximum values are cleared, and the servo-driven pen arms are recalibrated.

I have recently used this hygrothermograph to monitor and record the humidity and temperature within a humidity chamber during a treatment. The extension cable enables the sensor to be placed within the chamber while the recorder is mounted on the wall near by.

The Model CT485RS High Performance Microprocessor-Based Temperature/Humidity Recorder comes with batteries, the 6 foot remote sensor cable, AC adapter, 2 sets of pens, 120 charts (20 of each permutation), and an operator's manual; and is available from:

Omega Engineering, Inc.
P.O. Box 4047
Stamford, CT 06907-0047
(800) 826-6342

The list price is: $497.00 for charcoal grey or $525.00 for almond.

Chris Stavroudis, Paintings Conservator

The unit that is whipping me into a frenzy of consumer-lust is the ACR XT-102 Stick-On Logger, a pocket-sized datalogger that can be attached to a wall or exhibit case, or included in a shipping container, to gather temperature and relative humidity data for periods as long as six months. Powered by a lithium battery with a ten-year life, it will record data continuously at user-programmable intervals between 8 seconds and 20 minutes, has no moving parts, switches or visual displays. As with conventional dataloggers--and unlike hygrothermographs--the recorded data can then be downloaded into a microcomputer for analysis, storage, comparison, graphing, etc., software for which is supplied by ACR. In addition, the data can be exported to a spreadsheet for further crunching. Additional software, called Expert Extension Software is available for more involved statistical breakdowns. Here are a few specs for appetite-wetting purposes:

    Size:          3.25" x 2.38" x 0.63"
    Weight:        4 oz.
    Type:          Thermistor (10k ohms at 77 Deg.F.)
    Range:         -40 to 158 Deg.F. (-40 to 70 Deg.C.)
    Accuracy:      +/- 1 Deg.F. at 77 Deg.F.
    Resolution:    0.6 Deg.F.
    Response Time: 5 minutes (in still air).
    Range:         10 to 90% RH
    Accuracy:      +/-3.5% F.S.
    Response time: For a condition of no ventilation, and an
                   increasing RH excursion, the RH sensor has a
                   response time of 40 seconds or better for a 63%
                   change in RH. Adequate ventilation decreases the
                   response time.

The Stick-On Loggers (there are several other models available for other recording applications) require an IBM PC compatible with 512K, a graphics adapter and a serial port. If these units live up to their promise, they could be a very popular item among conservators. They are available from: Young Environmental Systems, LTD

P.O. Box 395
Manhattan Beach, CA 90266
(213) 676-9684 (fax)

Rustrak, a familiar name in the hygrothermograph biz, offers a very nice little portable datalogger, the Rustrak Ranger which is about the size of an old fashioned transistor radio. It handles four channels so you can plug in a variety of sensors or signal conditioners, including a combination temperature/relative humidity probe, a thin microphone-like cylinder 7 inches long that uses 2 of the channels. Rustrak, in techno-quaint mode, calls these Data Input Pods.

After recording for any duration between 10 minutes to 100 days, you can download the data into an IBM PC compatible where Rustrak's Pronto software handles data storage and retrieval and rather sophisticated graphing. For example it is quite easy to superimpose graphs of data from different recording sessions, to run min/max graphs, cumulative plots and histograms and all the other techniques that impress the shirts off the board of trustees. For heavier-duty number crunching, the data can be exported for use in spreadsheets, databases, mixmasters, etc. The Rustrak Ranger uses an adaptive memory system to provide optimum resolution and accuracy for varying recording times. It is programmed via an easy menu-driven system and all-told is a very nice package. My only real complaint is that, unlike the ACR instrument, the software comes bundled with it, so if you buy more than one unit you are stuck paying for extra copies of the software. My lab just bought 6 of these, and those expensively unnecessary disks rather bug me. On the other hand, they seem to work well and when I thought I had a problem with them, the company sent out a rep the next day (the instruments were blameless).

The instruments can also be used for realtime measurements, for those of you into the more meditative aspects of meteorology.

    Sampling rate:      654ms. Data Storage is automatically adapted
                        to suit recording period and the dynamics of
                        the signal
    Input range:        0-2 Vdc, maximum input +/- 3 Vdc
    Sensitivity:        0.5 mV
    Resolution:         +/- 0.5 mV
    Clock accuracy:     0.002% per year
    Recording time:     Programmable from 10 minutes to 100 days
    Output:             RS-232C programmable baud rates of 300, 1200,
                        4800, and 9600
    Power:              3 AA size rechargable Ni-cad batteries,
                        operational time between recharging depends
                        on the number and type of active channels.
                        Typical operational time 50-70 hours.
                        Optional battery pack allows for 30-45 day
                        operation. A separate but not-really optional
                        battery charger can also be used as an AC
                        adapter for long-term recording.

    Operating Temp.:    14 - 140° F
    Relative Humidity:  2 - 9% non-condensing

The Rustrak Ranger requires an IBM PC compatible with 256K ram, a graphics adapter of any sort, DOS 2.02 or later, and a serial port. If you have an ega with a monochrome monitor, the software will run sortof, but it won't be fun. There is also a new improved model the Rustrak Ranger II, but it seems a bit overkillish for most conservation applications. For more information, assail

Rustrak Instruments
1015 East Chapman Ave, Suite 210
Fullerton, CA 92631
(714) 631-0379

Walter Henry

MSDS Dictionary

Genium Publishing Corporation offers an excellent pamphlet called MSDS Pocket Dictionary, which covers 550 terms and abbreviations commonly encountered in material safety data sheets (a dark and arcane territory if ever there was one). The minimum order is 10 copies for which the cost is $37.30. Well worth getting some friends together for a group order. Genium Publishing Corporation

Room 128
1145 Catalyn Street
Schenectady, NY 12303-1836
(518) 377-8854 (518) 377-1891 (fax)

Surgical Gloves

Perhaps it's because I have longish nails, or perhaps I'm just prone to wanton acts of irrational violence in the lab, but I have always been very hard on surgical gloves. Recently, the mail brought a sample of Pure-Touch Powder Free Latex Gloves and, while I was finally able to savage them, it took some doing. Sensitivity is quite good, far superior to the wimpy things I am used to. They are available in Small, Medium and Large and come in Zip-lock bags packed 100 gloves per bag. A case of 10 bags sells for $95, which comes to 9.5 cents per glove. The stock number is 1500PF.

Infection Control Products, Inc.
894 Lincoln Avenue
Bohemia, NY 11716 (800) 829-2221

Maypon 4C Now Available From Conservation Materials, Ltd.

Maypon 4C (manufactured by Inolex Chemical Co.) is a anionic detergent based on the triethanolamine salt of hydrolyzed animal protein (yuck). It is the industrial replacement for Lexein S620 which has been published by Richard Wolbers, Professor, Art Conservation Program, University of Delaware, ("Aspects of the Examination and Cleaning of Two Portraits by Richard and William Jennys", AIC Preprints 1988, pp. 245-260) as the detergent in a surface cleaning gel. Maypon has a very high HLB (a very powerful detergent) and being based on a protein source, has an affinity for proteinaceous surfaces. It has a pH of 7-8 out of the bottle and can be used at any pH above 6.5.

As surface grime often is bound by environmentally borne protein, the Maypon works remarkably well as the basis of a surface cleaning system. A gel based on Richard's published formulation is:

    4 g       Maypon 4C
    2-4 ml    Benzyl Alcohol
    1.5 g     Hydroxypropylmethyl Cellulose
    100 ml    pH Buffered Distilled Water

Many options are available for the buffered distilled water, but I would recommend a 3% solution of triethanolamine to which acetic acid has been added to bring the pH to the desired value. pH paper with 0.5 pH unit resolution is acceptable for setting the pH, but an inexpensive pH meter with 0.1 resolution is better. At a pH of 7.5, the gel is very mild; at 8.5, it is slightly more aggressive. The pH should not be increased (made more alkaline) than 8.5 without careful consideration being given to the consequences.

To make the gel, Maypon 4C is dissolved in distilled water and then buffered. The HPMC is vigorously stirred into the soap solution avoiding the formation of clumps. After a few hours, when the HPMC has dissolved, benzyl alcohol is stirred in just to the point of clouding the solution (clouding means the limited solubility of the benzyl alcohol has been exceeded). Two somewhat more aggressive gels (i.e. effective, when safe to use) can be formulated based on a Carbopol thickened gel--the milder does not contain benzyl alcohol:

4 g       Maypon 4C
7 g       Carbopol-Triethanolamine stock gel
100 ml    pH 8.5 Buffered Distilled Water
(3-5 ml   Benzyl Alcohol, opt.)

The directions for making the Carbopol stock gel appeared in the May 1989 WAAC Newsletter (vol 11, no 2) (5g Carbopol 934; 65 ml distilled water; c. 12 ml triethanolamine). The stock gel, with the pH adjusted to 8.5, is cut into the Maypon and distilled water buffer (3% triethanolamine, adjusted to pH 8.5 with acetic acid) and allowed to stand until a smooth gel is formed. The gel may be used as is, or with the benzyl alcohol added as described above.

All of the Maypon 4C gel formulations listed above are generally mild and relatively safe for most surfaces that are not sensitive to water. Properly clearing the gels is very important, particularly so with the Carbopol. Spit or a dilute buffer solution (at the same pH as the gel) work effectively to remove the gels. For more information on the issue of clearing, please see the Letters section, page 31, in this issue. Because of its affinity for protein, Maypon 4C will often aid in the solubilization of old glue residues with nearly the effectiveness of an enzyme. (Note that it works by assisting the protein into solution rather than by hydrolyzing the protein as an enzyme does.)

Chris Stavroudis, Paintings Conservator

Carbopol 934
Ethomeen C25
Ethomeen C12
Armeen CD
Now Available From Conservation Materials, Ltd.

Carbopols (B.F. Goodrich Company) are a family of acrylic acid polymers that can be used to thicken both aqueous and solvent solutions. Richard Wolbers has formulated Carbopol into cleaning systems as a means of realizing the selectivity and specificity possible with his new approach to the cleaning of paintings. By gelling organic solvent mixtures, both the solvent properties and the handling properties are modified. Gelled solvents can be thickened to near solidity, thus controlling the evaporation rate, extending the contact time with the surface, and controlling the degree to which the solvent permeates the structure of the art work.

After having gained control of the physical application, the dissolving power of the solvent or solvent blends can be tailored with the goal of developing an ideal solvent for a particular problem. The art and science of arriving at that ideal solution to a particular cleaning problem is well beyond the scope of this note, however the mechanics of producing a gelled solvent is of general interest.

To be exploited as a thickening agent, the acrylic acid groups in Carbopol have to be made compatible with the liquid, allowing the polymer to unfurl thereby imparting a structure to the solution. To thicken a water-based system, the Carbopol need only be dispersed and then neutralized with triethanolamine (see above formulations) or ammonia. While any base will do, strong bases like sodium or potassium hydroxide are not recommended for conservation uses.

Making solvent gels is a trickier matter. The polarity of the final solvent solution must be compatible with the polarity of the final state of the Carbopol. The polarity of the Carbopol is controlled by the choice of neutralizing agents. While there is a wide range of possibilities for neutralizing agents (see Carbopol Water Soluble Resins printed and distributed by The BF Goodrich Company, Specialty Polymers & Chemicals Division), deft manipulation of only a few is all that is necessary to gel almost anything that would be used in conservation.

Very polar organic solvent and water blends (1:1 mixtures of water with acetone or ethanol) may be gelled with Carbopol neutralized with triethanolamine (or Ethomeen C-25, see below). Less polar solvent blends require that the Carbopol be neutralized with Ethomeen C-25 (Akzo Chemical Inc.), a cocamine substituted with 15 polyoxyethylene units. Ethomeen C-25 is a cationic detergent with a basic (the amine) group which can react with the acid groups on the Carbopol chain.

Ethomeen C-25 thickens a broad range of solvents from less polar blends of polar solvents and water (70% acetone or isopropanol, 30% water); to nearly pure polar solvents (90-95% ethanol or acetone); to mixtures of polar solvents, some non-polar solvents, and water (80% ethanol, 10% xylene, 10% water).

More non-polar solvent blends can be gelled with Ethomeen C-12 or Armeen CD (cocamine substituted with 7 polyoxyethylene units and pure cocamine, respectively). While it is a bit of a trick, VM&P Naphtha can be gelled with Carbopol and Armeen CD and a few drops of water.

The Carbopol/amine interaction is an acid/base neutralization, therefore some water must be present to allow the reactions to occur (and, for that matter, for the terms acid and base to have any meaning). The difficulty is adding just enough water to allow the neutralization reaction to take place without adding too much and forming an emulsion. The solvent gels should be clear or very nearly so.

Richard has developed the following gelling strategy. Pre-measure and combine the solvent components of the gel. Weigh out the Carbopol. Measure the amine. Add the amine to the Carbopol and stir until a smooth paste has been formed. This must be done in short order as moisture absorbed from the air can cause the Carbopol/amine to begin to thicken and spoil the gel. The solvent is added to the paste and the mixture is stirred constantly, either by hand or with an explosion proof, heavy duty stirrer (typically an air driven paddle stirrer). A magnetic stirrer cannot be used as it will stall as the gel thickens. When the Carbopol and amine are dispersed in the solvent, water is added in small amounts and slowly to the mixture.

As the gel begins to thicken, allow more time between additions of water. If the solution seems to stop getting thicker, or if it becomes cloudy, try adding a bit more of the amine. After the gel has formed, additional water, if compatible with the polarity of the gel, can be mixed in. If the gel is too thick for your tastes, add more of the starting solvent mixture--a bit more water may be required too.

The proportions of materials are: for 100 ml final gel volume, use 1.2g of Carbopol, 4 ml of Ethomeen C-25, and about 5 ml of water. If Armeen CD is used, start with 5 ml.

Notes on clean-up:

Carbopol will effectively gel your plumbing if carelessly washed down the drain. Always dispose of solvent charged gels as you would for solvents. Spoiled Carbopol/amine mixtures (the muck at the bottom of the beaker when the gel doesn't form properly--it happens to all of us now and then) should be allowed to dry and then disposed of as solid waste. Residue inside beakers should be wiped out before washing. Containers used with the gels or the non-neutralized Carbopol should be washed in water with a nonionic detergent and a bit of ammonia added. Should your drain begin to run slowly, try flushing it with copious amounts of dilute ammonia and nonionic detergent.

The Ethomeens and Armeen must be acidified to be dissolved in water, so wash those containers in a dilute acetic acid solution. The un-neutralized amines are quite caustic, so proper care in handling must be observed.

Chris Stavroudis, Paintings Conservator

DISCLAIMER: Many of the materials discussed above pose safety and health hazards to the conservator. It is the responsibility of each conservator to familiarize themselves with any special handling procedures necessary with these materials. Consult Material Safety Data Sheets, and read any and all cautions. The above listed formulations are presented to provide an exchange of information between conservators. The authors, sources, and/or WAAC cannot be responsible for any undesirable outcome experienced by another practitioner. Further, it is not intended for any person who is not a trained conservator to use these formulae on works of art.

New Distributor for Lascaux

Conservation Materials Ltd. has announced that they are now the U.S. Stocking Distributor [only my intense professionalism forces me to let such a straightline pass--ed.] for Lascaux Restauro materials manufactured in Switzerland by Alois K. Diethelm AG. The initial stock will consist of

Conservation Materials will be adding products from the Lascaux line as U.S. conservators request them. They have a great deal of technical information about these products and it is yours for the asking.

Gel Loading Pipet Tip

GEL-SAVER Gel loading pipet tips from USA/Scientific Plastics are the kind of tools that just about scream to be used in conservation work, if someone clever can just figure out something to do with them. Designed for use with micropipetters in DNA/RNA sample manipulation, these virgin polypropylene pipet tips have a final delivery orifice of less than 0.25 millimeter O.D. The tips are very soft and remarkably flexible (one could probably knot them), and could certainly be used to deliver relatively unviscous liquids behind flaking paint and that sort of thing. Designed for use with the Eppendorf Ultra Micro Pipettor, Pipetman P-20, and the USA 1259 Micro-Volume Pipettor (from the same manufacturer at $190), they are sold in racks containing 204 tips at $28 per rack. If anyone can find an application for these tips, please pass them on to the Technical Exchange.

USA/Scientific Plastics
P.O. Box 3565
Ocala, FL 32678
(904) 351-2057 (fax)

The Featured Catalog

For this issue, the featured catalog just barely qualifies as a catalog at all; it is really just a small but enticing advertising sheet and price list. Minitool, Inc offers a variety of small, fairly inexpensive hand tools and other items designed for micro-electronics and miniature applications. Some of the zippier items are a set of miniature measuring scales for use under a microscope ($10-15); a microlapping kit for ultra-fine polishing, which accommodates five different abrasives from 600- 20,000 grit ($30); and several sets of miniature tools, such as needle probes, scribers, chisels, scrapers, etc. ($9-28) Minitool, Inc.

1334 / F Dell Avenue
Campbell, CA 95088
(408) 374-1585 or
(408) 374-1587
(408) 374-2917 (fax)

Lead Rings

Donut-shaped vinyl coated lead weights are intended to be used to add stability to flasks, graduated cylinders and the like, but also serve effectively as weights for conservation treatments. For example, the donut's hole can be used to provide differential pressure and tension for reducing planar distortion in paper, or to avoid weighting a sensitive area. Available in weights from 0.5 lbs (1 7/8 inches I.D.) to 2.0 lbs (2 7/8 inches I.D), the cost is $11-20.

Whatman LabSales
P.O. Box 1359
Hillsboro, OR 97123-9981

Walter Henry, Conservator
Technical Exchange Column Editor

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