Northern States Conservation Center

Providing collection care, preservation and conservation treatment services to collectors and collecting institutions.



  • CCI Light Damage Slide Rule. Available from Northern States Conservation Center, P.O. Box 8081, St. Paul, MN, 55108. Phone: (651) 659-9420. web:
  • Internally filtered flourescent bulbs with high color-rendering capacity. Available from Verilux, 9 Viaduct Road, Stamford, CT, 06907. Phone: (203) 921-2430 x 103 (Sales). fax: (203) 921-2427.
  • Polypropylene mats. Available from Consolidated Plastics Company Inc., 8181 Darrow Road Twinsburg, OH,, 44087. Phone: (800) 362-1000, fax: (330) 425-3333, web:
  • Information on fire protection. Available from the National Fire Protection Association (NFPA), 1 Batterymarch Park, PO Box 910, Quincy, MA 02269-9101, phone: (800) 344-3555, web:
  • "Stuf-it" copper wool gauze. Available from Allen Special Products Inc., 1610 Bethelem Pike #B3, Hatfield, PA 19440-1602, phone: (800) 848-6805 or (215) 997-9077.

Collections Caretaker

Vol.2 No.4 Summer 2000 Preservation in Storage Design
Consider preservation in storage design by Catharine Hawks
A simple, quick mount briefly displays clothing for the Science Museum of Minnesota by Gretchen Anderson
Display mounts for marine mollusks by Brad Bredehoft

Consider preservation in storage design

by Catharine Hawks

Many museums eventually have the opportunity to build or renovate their storage. A few simple guidelines can help improve storage spaces, especially for scientific specimen collections and objects. Good design, coupled with appropriate maintenance of the finished areas, promotes the long-term care of a collection. there are two key concepts:

  1. Storage areas are not meant to be inviting.
  2. Storage areas should be easy to monitor and clean.

Construction Considerations

  • Plan for segregated storage rooms. Collection storage space should not be used for any function other than breif curatorial and collection care activities.

  • Provide 350 pounds per square foot floor loading for compact or mobile storage systems. This also will permit cabinets, collections on pallets, or objects in crates to be moved safely using lift equipment such as pallet trucks. Corridors between freight elevators, storerooms and exhibit areas should have similar floor loading capacities.
  • Ensure that the entrance to any storage area is wide enough and tall enough to accommodate full cabinets and the large objects.
  • Install keycode or other electronic entry controls at storage room doors. If electronic security is not possible, use a highly restricted key system for entry (Keller and Willson 1995, Kelly 1998). Consider adding a security window to the door to permit inspection of the room from the exterior. For easy inspections, lighting should turn on from outside the room.
  • Avoid dropped ceilings. Dropped ceilings provide pest habitat, disguise leaks, and generate dust and debris that foul air filtration systems.
  • Equip storerooms with water-based, automatic fire suppression systems and plan for regular maintenance. Individually active heads are best. Do not use dry pipe systems unless pipes might freeze. Mist systems are not proven effective against fire and may not meet fire codes. Gas systems are more damaging to collections and staff than water based systems (Wilson, 1995).
  • Label pipes and ductwork so that staff can protect collections stored below. Ideally, minimal ductwork and no pipes, other than sprinkler lines, are in storage rooms.
  • Install seals around duct and pipe chases where they pass through storeroom walls, floors, or ceilings. Stuf-it copper wool gauze will keep insects from using these gaps to reach the collections.
  • Avoid interior duct linings. Where needed for noise control or to reduce condensation, use external duct linings.

Climate control

  • Install climate control equipment outside storage rooms, so maintenance workers will not need to enter and equipment leaks will not affect the collection.
  • Filter incoming and recirculated air to the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 90-95% level. Externally generated particulate pollutants are far more damaging to collections than externally generated gaseous pollutants, mainly because the particulates adsorb gaseous pollutants and hold them directly on objects or specimens. Also particles can etch, abrade and obscure fine details.
  • Plan for a moderately dry environment. The relative humidity (RH) range most suited to the majority of natural history collections is 40-60%, assuming the building fabric is designed for this range (Conrad 1995). If storage room environments are 30-65% RH over the course of a year, specimens and objects inside well-sealed cabinets can survive because the RH inside the cabinets will be between 45% and 55%. Some materials are sensitive to mechanical damage at RHs below 40%, (teeth, bone, and shell). At RH fluctuations below 40% these materials will crack and spalling (Williams 1991, Morton 1996). There are some collections that benefit from low RH, for example, film based photographic materials (Nishimura 1995); fossil and mineral specimens that contain reactive iron sulfides (Howie 1992); and paper based archival materials (van der Reyden 1995). Discussion of the impact of humidity levels on various collection materials is given by Alten (2000).
  • Plan for a moderately cool environment. While temperature is less important than humidity for most collections, the rate of chemical degradation of organic materials doubles with every 18°C rise in temperature. A temperature range of 65-70°F, although it is cooler than the normal human comfort level, still allows staff to work safely without numb fingers. Film based photographic materials require both low temperatures and low humidity for good preservation (Reilly 1993, 1998).
    For fluid-preserved collections, relative humidity is unimportant as long as it is not above 65% (high RH promotes corrosion of glass and metal lids or bails). For fluid-preserved specimens of all kinds, the primary concern is that temperature be constant. Changes in temperature cause pressure changes that result in damage to container seals, allowing storage fluids to evaporate (Simmons 1995). For collections that are not fixed in formaldehyde prior to storage in alcohol solution, a steady, low temperature (above freezing) aids preservation. For specimens fixed in formaldehyde solutions and stored in formalin or an alcohol, keep a steady temperature not lower than about 65°F. Lower temperatures cause formaldehyde removal from the tissues, allowing them to deteriorate (Simmons 1995).

Storage lighting

  • While visible light is responsible for much fading and color change, ultraviolet (UV) radiation causes cleavage of the chemical bonds in organic materials. At high light and UV intensities, damage to organic materials can occur quickly. This is illustrated by the CCI Light-Damage Slide Rule (see resource list).
  • Install flourescent fixtures as indirect lighting, bounced from ceilings and walls to illuminate an area.
  • Filter fluorescent lights to remove UV. No filter is completely effective. The best filters reduce UV levels to 0-10 microwatts (µW)(Michalski 1994).
  • Use lighting with a high color rendering index (CRI). One can see well under low-intensity lights with high CRI.
  • Light intensity is a factor in UV-caused damage (Michalski 1994). Three hundred lux light intensity allows any age viewer to see well in storage.
  • Paint walls and ceilings white or a light color. White reflects most light, allowing lower intensity lighting in work or storage areas. White or light walls and ceilings permit easy dust, cobweb and insect monitoring. Use paint with tiatnium dioxide. It absorbs some ultraviolet radiation, reducing UV in reflected light. Avoid oil based paints, single component epoxies, alkyd paints, or oil-modified polyurethane coatings, which produce damaging fumes. Use an acrylic or acrylic urethane coating for the walls (Tetreault 1999).
  • Coat cured concrete floors with a solvent-borne epoxy sealer, topped with a moisture-cure epoxy sealer, and avoid all other floor coverings (anything else will require wet cleaning or will be a source of particulate or gaseous pollutants). When worn, the topcoat can be replaced without evacuating collections from the area. Use clear or pigmented epoxy. Do not use white, it will always appear scuffed.
  • Install polypropylene fiber mats outside storage room doors to reduce dust tracked into the rooms.

Catharine Hawks is a conservator in private practice specializing in objects and natural history specimens. She can be reached at 2419 Barbour Road, Falls Church, VA, 22043-3026. Phone: (703) 876-9272, e-mail:


Alten, Helen. 2000. How temperature and relative humidity affect collection deterioration rates. Collections Caretatker 2(2): 1-3,6-7

Conrad, Ernie. 1995. A Table for Classification of Climatic Control Potential in Buildings. Landmark Facilities Group, Inc., Norwalk, CT.

Howie, Frank.1992. Pyrite and Marcasite. Pp. 70-84 in The Care and Conservation of Geological Material: Minerals, Rocks, Meteorites and Lunar Finds (F. Howie, ed.). Butterworth-Heinemann, London.

Keller, Steven, and Darrell Willson. 1995. Security systems. Pp. 51-56 in Storage of Natural History Collections: A Preventive Conservation Approach (C. Rose, C. Hawks, and H. Genoways, eds.), Society for the Preservation of Natural History Collections, Iowa City.

Kelly, Wayne.1998. Security Hardware and Security System Planning for Museums. Technical Bulletin 19. Canadian Conservation Institute, Ottawa.

Michalski, Stefan. 1994. Controlling UV Damage. Canadian Conservation Institute, Ottawa.

Morton, Joanna. 1996. Conservation of Molluosc Periostraca: A Preliminary Investigation into Relative Humidity Conditions and Coating Materials for Preservation of Periostraca. Report prepared as part of the curriculum for the University of Canberra, National Center for Culture Heritage Science Studies, Conservation of Cultural Materials Program, Canberra.

Nishimura, Douglas. 1995. Film supports: negatives, transparencies, microforms, and motion picture film. Pp. 365-393 in Storage of Natural History Collections: A Preventive Conservation Approach (C. Rose, C. Hawks, and H. Genoways, eds.). Society for the Preservation of Natural History Collections, Iowa City.

Reilly, James. 1993. IPI Storage Guide for Acetate Film. Image Permanence Institute, Rochester, NY.

Reilly, James. 1998. Storage Guide for Color Photographic Materials. Image Permanence Institute, Rochester, NY.

Simmons, John. 1995. Storage in fluid preservatives. Pp. 161-186 in Storage of Natural History Collections: A Preventive Conservation Approach (C. Rose, C. Hawks, and H. Genoways, eds.). Society for the Preservation of Natural History Collections, Iowa City.

Tétreault, Jean. 1993. Measuring the acidity of volatile products. Translation from, "La mesure de l'acditité des produits volatils," which was originally published in 1992 in Journal of the International Institute for Conservation-Canadian Group 17: 17-25.

Tétreault, Jean. 1999. Coatings for Display and Storage in Museums. Technical Bulletin 21. Canadian Conservation Institute, Ottawa.

van der Reyden, Diane. 1995. Paper documents. Pp. 327-353 in Storage of Natural History Collections: A Preventive Conservation Approach (C. Rose, C. Hawks, and H. Genoways, eds.). Society for the Preservation of Natural History Collections, Iowa City.

Williams, Stephen. Investigation of the causes of structural damage to teeth in natural history collections. Collection Forum 7(1): 13-25.

Williams, Stephen, and Suzanne McLaren. 1990. Modification of storage design to mitigate insect problems. Collection Forum 6(1): 27-32.

Wilson, Andrew. 1995. Fire protection. Pp. 57-79 in Storage of Natural History Collections: A Preventive Conservation Approach (C. Rose, C. Hawks, and H. Genoways, eds.), Society for the Preservation of Natural History Collections, Iowa City.

A simple, quick mount briefly displays clothing for the Science Museum of Minnesota

by Gretchen Anderson

A simple padded T-mount became a flexible and useful display system for a three-day traveling exhibit from the Baseball Hall of Fame. Because the baseball jerseys arrived shortly before installation, the mounts had to be quick-to-construct, inexpensive and flexible.

All of the materials for the structure can be found at a good hardware store: polyvinyl chloride (PVC) pipe (1-1/4" and 1-1/2" diameter), PVC fittings -- a 1-1/4" "T" connector and a 1 1/2" pipe straight connector -- PVC cement, metal floor flange and threaded connector to fit the PVC connector, bolt with wing nut and plywood. Padding materials came from a fabric store, conservation suppliers and medical suppliers: polyester batting, cotton stockinette (2 inches & 4 inches), scraps of one-inch polyethylene foam and clear hot melt glue. The estimated cost was $20.00 per mount.

PVC plumbing pipe and attachments were easy to find locally. PVC does not age well, but for a three-day exhibit, we were not concerned about acidic fumes produced as the plastic deteriorates. If you construct this mount for more permanent display, consider using ABS plastic plumbing pipe or metal piping. Here is how each mount was constructed:

  1. We cut a wide and a narrow pipe 23 inches long for the upright pole. The narrow pipe inserts and slides easily inside the wider pipe. The length was determined by the minimum and maximum heights needed. Twenty-three inches allows for a full extension to about 40 inches. One end of the wide pipe was adhered with PVC cement to the unthreaded end of the straight connector. The threaded end will attach to a flange, so the pipe stands upright.
  2. Two arms seven inches long were cut from narrow pipe. The arms joined to the two sides of the T connector. The bottom of the T connector was attached to the 23 inch long narrow pipe. We found that seven inches was a good size for the baseball jerseys. Determine the arms' length by the desried overall width.
  3. With the narrow pipe removed, drill holes (larger than the bolt diameter) completely through the wider pipe at one inch intervals. Make sure the bit is at right angles to the pipe, so holes are not slanted. Insert the narrow pipe and redrill the holes. It is important that inner and outer pipe holes line up. By shifting the inner pipe, the length of the rod can be changed. Measure the length of your garment and adjust the mount height. Insert the bolt through the holes in the large and small pipes and secure with a wing nut.
  4. Cut a plywood base 20 inches by 20 inches. Mount the metal flange in the middle. Alternatively, mount the flange directly on the exhibit case floor. Screw the wide pipe into the flange to install the mount.
  5. The top of the T was padded to support shoulders. Padding and dimensions varied according to the shirt. Use one-inch polyethylene foam, attached with hot glue, to pad the top of the mount. Cut the foam to an approximation of the garment's shoulder profile before attaching it to the top of the T. Wrap polyester quilt batting around the mount to soften edges.
  6. Cover the padding with washed, four-inch cotton stockinette - one piece over each arm and whip stitched together in the center. Leave the ends open to adjust padding.
  7. Cover the upright pole with washed two-inch cotton stockinette long enough to cover the support when raised to its full height. Wrap the pole with a thin layer of batting and cover with more stockinette.
  8. Place the garment on the mount, padding arms and chest as needed. Use small stockinette or muslin pillows stuffed with polyester batting to fill out the chest, sleeves and back. Sew the pillows to the mount or attach with velcro.
  9. Drape visible parts of the mount with a nice exhibit fabric.

This mount was a group effort. Special thanks to the staff and voluntters who helped.

Gretchen Anderson, Objects Conservator at the Science Museum of Minnesota, holds an MFA in Museology and Art History from the University of Minnesota.

    Available at a good hardware store:
  • PVC pipe (1-1/4 inch and 1-1/2 inch diameter)
  • PVC fittings - a T connector for 1-1/4 inch pipe and a straight connector for 1-1/2 inch pipe with one end threaded
  • PVC Cement
  • Metal floor flange to fit the PVC connector
  • Bolt with wing nut
  • Plywood
    Available at fabric stores, or through conservation and medical suppliers:
  • Polyester batting
  • Cotton stockinette, a tubular cotton knit (two inch and four inch)
  • Scrap one inch polyethylene foam
  • Hot melt glue
  • Drill
  • Saw
  • Pipe cutter
  • Clamps
  • Hot glue gun
  • Neddle and thread
  • Scissors

Display mounts for marine mollusks

by Brad Bredehoft

Museum exhibits regularly include animal mounts. Deer heads, bird species, and even dinosaur skeletons are common. But then there are mollusks.

The Science Museum of Minnesota recently devised display mounts for 250 shells, including bivalves such as clams and univalves or snails.

The shells were mounted at a 20-degree slope in floor cases. The shells were ordered by family groups with quarter-inch gaps between individual family mounts (see picture of finished case).

The challenge was to display the shells to show as much of each as possible, while keeping them from sliding off the angled display surface, without using adhesive.

The display had to protect the shells from light as well as acidic environments, because such factors accelerate deterioration. Shells are light sensitive, easily abraded, broken or stained.

Quarter-inch foam was used in two layers under each family group. The bottom layer was unchanged, providing a flat, even base, while the top layer was cut into or built up to support the shells. The shells were individually mounted as dictated by the characteristics of each. Foam support structures were joined together with hot glue. The heavier shells were given points to lock them into position.

Most of the bivalves simply rest on top of individually carved foam structure or in a well carved into the top layer. Many of the univalves fit over or twist onto a foam structure. In one situation museum wax was required to hold a Nautilus shell's large opening in an upright position, as it would float in the ocean. Gravity favors the opposite orientation.

After the shells were fitted to their mounts, they were removed. The carved foam was commercially flocked using black polyester adhered with a polyvinyl acetate PVA emulsion called Flexglue. After flocking the shells were placed on their mounts with minimal adjustments needed. The black-flocked foam resembles a fabric covered mount.

Medium-density-overlay (MDO) board supports the mounts. was covered with Marvelseal to act as a vapor barrier and reduce acid fumes from the wood from harming the shells. Marvelseal was ironed onto the MDO to reduce acid fumes from the wood. The outside edges ans spaces between individual shell families were covered with commercially available black seam binding using doublestick tape to mask the Marvelseal from view. Finally the foam mounts were attached to the covered board using doublestick tape.

The final result was time consuming, but created a sharp looking display. The marine mollusk's colors stand out against the black-flocked background. Marvelseal reduced acid vapors effectively, as verified with acid detection (A-D) strips.

Brad Bredehoft, Webmaster for the Science Museum of Minnesota, has also worked for the Science Museum in exhibition packing, object transport and display fabrication.

  • Double stick tape (ATG 3M 969)
  • Hot melt glue
  • Museum wax
  • Insect pins
  • Marvelseal (a polyaluminum laminate)
  • White quarter-inch closed cell polyethylene foam called Zotefoam. (Black foam is a good alternative.)
  • Black seam binding
  • Polyester flocking
  • Exacto knife
  • Hot glue gun

P.O. Box 8081, St. Paul, MN 55108   Phone: (651) 659-9420

© 2002 Northern States Conservation Center

Updated 11 May 2002