Fluid Preserved Specimens


Beginning in the 17th century, researchers and museums have been able to preserve whole specimens by submersing and storing them in fluid chemicals. There are three components to a fluid-preserved specimen:

  • The fixed specimen: The specimen is prepared by “fixing” it, achieved by injecting it with chemicals that stop the deterioration and decay process (known as “autolysis”). The most common fixative is formaldehyde, or a formaldehyde and water solution known as formalin. Some specimens may not be fixed before being submersed in the fluid preserve.
  • The fluid preserve: The preserve is commonly alcohol, either ethanol or isopropyl alcohol.
  • The container: Containers are typically glass jars or bottles sealed with a closure. Types of closures may vary within a collection and often include lids with gaskets. Large specimens may require the use of open glass tanks.

Although the fixative and fluid preservation process causes a chemical alteration of the specimen and can lead to discoloration, shrinking, or swelling of the specimen, these collections are able to last for hundreds of years.

Staff members working with these collections are not generally at risk of chemical injury from the fluids unless a jar breaks. The greatest hazard of fluid-preserved collections is the flammable nature of the chemicals. A build-up of fumes will increase the chances of a fire.

Commonly Treated Items:

The most common animals to be preserved in fluid are aquatic invertebrates (mollusks, crustaceans, etc.),Herpetology (reptiles and amphibians), and Ichthyology (fish). Some entomology specimens may also be fluid preserved. Other materials may be stored in fluids, such as plants, and minerals.


Storage jars should be monitored for deterioration of closures (e.g. lids and gaskets) that would lead to leakage of flammable chemical fumes into the storage area. Open containers will continuously leak fumes into the environment, so the storage area should be well ventilated.


Exposure to formaldehyde and/or formalin can occur when initially immersing the specimen, handling the containers, topping off the fluid in the containers, or transferring the specimen to another solvent. Contact with lower concentrations may cause eye and skin irritations, while higher concentrations can cause more serious symptoms like pneumonia and pulmonary edema.


The following suggestions will help prevent breakage of the glass containers and the possibility of chemical spills, and will promote protection of the specimens and museum staff in the storage areas:

  • Storage shelves should be flat and level, preferably with a lip on the edge to keep containers from falling off and breaking.
  • Do not overcrowd storage shelves.
  • Ensure that all staff working with the specimens know proper handling techniques.
  • Use flammable materials signage in storage spaces. Set up appropriate fire equipment (such as sprinklers and fire extinguishers).

To protect from contact with formalin if a container does break or during transportation of the specimen from one solvent to another, always:

  • Wear personal protection equipment (PPE) to protect clothes and the body, such as disposable gloves, eye goggles, and when working with a large amount of solvent, a lab coat.
  • Install an eye wash station in storage areas.
  • Keep storage areas well-ventilated.
  • Keep formaldehyde spill kits accessible in storage areas. Kits are available for purchase on-line.

Institutions that re-use ethanol as the fluid preserve through an ethanol recovery system should follow guidelines set for the handling of hazardous wastes. The Environmental Protection Agency website outlines hazardous waste regulations.

Case Study: The American Museum of Natural History recently completed the C. V. Starr Natural Science Building that houses the Invertebrate Zoology alcohol-preserved collections in a 4,000-square-foot compactor facility with an adjoining laboratory area. The more than 700 cases in the unit allow for well-organized and secure storage in an environment of stable temperature and humidity. The museum equipped the storage area with several safety precautions that meet regulations set by the New York Fire Department, including:

  • Sprinkler system
  • Storage of materials at least one foot away from a sprinkler head to allow unimpeded water flow
  • Supply of fire extinguishers that are inspected annually by an outside source
  • Two-hour fire rated construction for the walls of the storage area
  • One and a half hour fire rated construction for the doors of the storage area
  • Automatic door closers on all doors
  • The use of flammable storage refrigerators only for alcohol storage
  • No smoking signage posted inside and outside the storage are
  • Hazardous materials signage posted outside the storage door

Additional Resources:

Several of the National Park Service Conserve O Gram leaflets listed in the section on Natural History Specimens provide specific information on this topic. Of particular interest on this topic are:

The Marine Biodiversity Processing Center of the Natural History Museum of Los Angeles County has an online library with a list of collection care publications including topics related to fluid preserved specimens. [http://collections.nhm.org/library/curation:curation]

Burroughs, Edward G. et. al. 2006. “Exposure of Museum Staff to Formaldehyde during some Wet Specimen Activities.” In Collection Forum. Vol. 20, no. 1&2. Pp. 49-54.

Marte, Fernando, et. al. “The Stability of Natural History Specimens in Fluid-Preserved Collections.” Smithsonian Center for Materials Research and Education, Suitland, Md.

Simmons, John E. 1995. “Storage in Fluid Preservatives.” In Storage of Natural History Collections: A Preventive Conservation Approach. Eds. Rose, Carolyn L., et. al. York, PA: York Graphics.

Standsfield, Geoffrey. 1984. “Conservation and Storage: Biological Collections.” In Manual of Curatorship: A Guide to Museum Practice. John M. A. Thompson, Ed. London: Butterworths. Pp. 289-295.