Volume 14, Number 2, May 1992, pp.24-25

Technical Exchange

Pottery Mending Clamp

There is a simple and effective way to eliminate the harshness of metal clamps and the awkwardness of small loose pieces of padding that are often needed when mending pottery vessels. Metal clamps are often necessary in holding joins together as the adhesive sets. However, these clamps tend to deface surface decorations. For the reassembly of large archaeological vessels at the Arizona State Museum, the following clamp proved to be an easy, useful and inexpensive alternative to a variety of metal clamps. The clamp consists of a carriage or eye bolt, a nut, 2 soft rubber washers, 2 thin metal fender washers, 2 disks cut from closed cell polyethylene foam (e.g. Plastazote or Voltek, available from packaging houses), and a wing nut. The size of the foam can be varied to accommodate different areas of coverage. The washers add additional support to the foam which will conform somewhat as the clamp is tightened. This is particularly useful in securing mends where sherds are missing and there is a strong curve to the vessel.

This simple clamp has one other nice feature: it's cheap.

Hot Tip

Inspired by Fonda Thomsen's article "Hot Melting Cutting of Stabiltex" [JAIC 27 (1988):32-37], which describes simultaneously cutting and hot melting the edges of polyester Stabiltex to avoid fraying, we sought a cheaper hot tip than the one recommended. Other textile conservators commented that the pen recommended in the article did not always give a smooth cut on curved edges. Delaware textile conservator Nancy Lee Papay suggested trying a Mylar cutter designed for making quilt stencils. At $31.95 one could hardly lose. For the Arizona State Museum's NSF sponsored Archaeological Textile Conservation Project, we ordered the stencil cutter with the fine tips and found this tool marvelous for cutting Stabiltex for backings (which were applied to the textiles with sewing techniques). By plugging the stencil cutter into a rheostat we could set the temperature control.

Combination Stencil Cutting Kit:

Item number: CSC120
The American Quilter
P.O. Box 7455
Menlo Park, CA 94025

The rheostat is Hot Tool, Inc.'s Dial Temp, which is part of a tape removal kit distributed by University Products (#425-1005).

Environmental Monitor

Exeter Environmental Systems offer the Hanwall Monitor, a data logger which provides recording measurement of temperature, humidity, lux, UV power, cumulative lux, and cumulative UV. Coupled with a separate handset via an infrared communication link (for a cable-free system) or through the serial port, it can communicate with a central pc, for environmental monitoring in a building or display case. It is possible to preset alarm levels so that out-of-range temperature at the remote location will trigger an alarm. Included in the cost of the unit is software that both controls the devices and provides graphical and statistical output.

The sensors are of the following types:

Temperature: Semiconductor
Humidity: Capacitive Polymer
Lux: Megatron Cosine-Corrected Cell
UV: UV-enhanced silicon photodiode fitted with broad-band UV filter

Costs:

Monitor: 965 Pounds
Handset: 850 Pounds

For more information:

Exeter Environmental Systems
Oriel House, 135 Topsham Road
Exeter, Devon EX2 4RE England
0647-24509 or 0392-426810 0392-410333 (fax)

UV Lights

Conservators looking for small UV lights may be interested in a pair of instruments from Ultra-Lum. Model UVA-006, a 6 watt portable/rechargeable, weighs 3 pounds (at 10" X 3" X 5.25") and runs for 5 - 7 hours on a charge. Model UVA-28T Blacklight Lamp, a larger plug-in unit, offers higher intensity illumination through dual 8 watt lamps. It weighs 2.5 pounds. The battery model lists for $139 and the plug-in for $185.

Ultra-Lum, Inc.
217 East Star of India Lane
Carson, CA 90746
213/324-2247 213/324-3318 (fax)

Elvace

For some time now, book conservators have reported difficulty obtaining Elvace 1875, a popular Vinyl Acetate-Ethylene Copolymer. Fortunately, Reichold reports that you can purchase Elvace 40705-00 directly from Reichold, even in 5 gallon quantities. For quantities less than 55 gallons, the price is $2.705 per wet pound. You will need to pay for shipping. 5 gallon quantities ship via UPS.

Janelle D. Brown
Sales Coordinator, Sales Service Team
Emulsion Polymers Division
Reichold Chemicals, Inc.
800 Capitola Drive
Durham, NC 27713
800/441-6461
P. 0. Box 13582
Research Triangle Park, NC 27709

See Update

A little historical note that may help clarify a common misunderstanding. Back in the days when Elvace was produced by Dupont, many book people were fond of Elvace 1874. When Reichold took over production they eliminated 1874, but kept 1875, which differs from the other product only in that it is of slightly higher viscosity. At this time 1875 was renumbered 40705-00.

The product bulletin provides the following description of Elvace 40705-00.

(please obtain an MSDS for more information on health issues)

  -------------------------ELVACE 40705-00------------------------

  Tough permanently flexible polymer film
  Excellent viscosity build with plasticizer addition
  Superior adhesion to packaging film and foil
  Poor borax tolerance
  Excellent resistance to plasticizer migration
  Short bond development times
  Greater resistance to hydrolysis when compared to a polyvinyl
       acetate homopolymer

  Typical properties
      * Nonvolatile content, %, Minimum:                     54.5
      * pH:                                             4.0 - 5.5
      * Viscosity, Brookfield RV#3 @ 20 rpm,
         25°. C / 77°. F, cps:                  1900 - 2800
      * Weight, U.S. lbs./gallon                        8.8 - 9.0
      * Glass transition temperature, by differential
         scanning calorimetry,°. C--
                           Onset                                O
                           Inflection                           6

  Storage: Protect from freezing. Ideal storage temperature is
       72°. F. Stability at 72°. F is more than 180 days.

  Packaging: Available in 10,000- or 20,000-gallon railroad tank
       cars, 5,000-gallon tank trucks, or 55-gallon nonreturnable
       steel or fiber drums.

  C.A.S. Number: Mixture
  HMIS Rating:      health=1       fire=O      reactivity=O

       Ingredients                 Content Limits   Max. Exposure
  Vinyl Acetate Monomer
        (CAS # 108-05-4)                  1.0%           10.0 ppm
  Ethylene-Vinyl Acetate Copolymer
        (CAS # 24937-78-8)               54.5%      None assigned
  Water (CAS # 7732-18-5)                45.5%      None assigned

  Physical Data
      * Boiling point:                               > 212°. F
      * Vapor Density:                           heavier than air
      * Volatile %:                               45.5% by weight
      * Specific Gravity:                                    1.07
      * Evaporation Rate:             slower than n-Butyl Acetate
      * Appearance:                 white liquid with acetic odor

  Fire and Explosion Hazard Data
      * Flammability Class:                                    3B
      * Flash Point:                                          N/A
      * LEL:                                                  N/A

  Health Hazard Data: Permissible Exposure Level: The ACGIH TLV
  and OSHA PEL for vinyl acetate are both set at 10 ppm for an
  8 hour TWA and at 20 ppm for the STEL.