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Colored Dots for Coding Fluid Collections


This system provides a rapid means of visually tracking the chemical history of fluid preserved specimens. It provides a way:

  1. to avoid having to smell a solution when a jar needs to be topped up
  2. to track the progress in transferring collections from isopropyl to ethyl alcohol
  3. to determine which specimens have been fixed in formalin
  4. to indicate specimens that need to remain in formalin as a preservative
  5. to identify storage solutions of material loaned from other institutions that are different than the in-house preservatives.

Visual scanning is important due to the sensitivity or allergic responses of many staff members to handling or being exposed to certain chemicals, especially formalin and isopropyl alcohol. To rely on having to sniff solutions to determine the contents of a specimen jar is a health hazard. Reading label information is too time consuming and often the labeling effort lags behind the transfer work.


F. G. Hochberg
Dept. of Invertebrate Zoology
Santa Barbara Museum
of Natural History
2559 Puesta del Sol Road
Santa Barbara, CA 93105 USA
Tel (805) 682-4711, ext. 318
Fax (805) 569-3170

Photograph: Henry Chaney

Publication: 1992


Small colored adhesive dots are applied to the lid of the specimen jar. The combination of colored dots allows a curator or collection manager to ascertain rapidly whether a specimen has been fixed originally in formalin, perhaps transferred later to 50% isopropyl alcohol and then subsequently transferred to 70% ethanol for long-term storage. Specimens on loan from another institution, especially those preserved in chemical solutions which differ from those used in-house, should be color coded on receipt in case solutions need to be topped up while in the care of the borrowing institution.

Soft-adhesive, foil backed color coding dots are used. These dots have a 1/4in diameter and come a variety of colors. Three colors are used routinely for standard solutions (e.g., one color for formalin, another for isopropyl alcohol, and a third for ethyl alcohol). The dots are applied to the top and to one side of a clean plastic lid (white polypropylene). As each chemical treatment is completed, the next dot is added and partially overlapped on top of the previous dot to indicate the sequence or history of the chemical treatment (Fig. 1). When the process is completed and the specimen resides in the final preserving solution the dots are coated with a thin layer of ethyl methacrylate/methyl acrylate copolymer adhesive to seal and protect the dots from contact with alcohol, which in some cases will cause the color of the dot to bleed.

Figure 1. Small colored dots are used to code the chemical contents of jars in a fluid collection. 
                Writing on the lid reinforces instructions or identifies loans and voucher specimens.

Materials Tools Supplies

  • Ethyl methacrylate/methyl acrylate copolymer adhesive
  • Foil-backed, colored adhesive dots, several sizes, 1/4in, 1/2in, 3/4in


The larger dots can be used in a variety of color combinations to indicate many things. For example, to track the source of voucher specimens from specific environmental survey projects where the specimens have to be kept separate from the main collections for a fixed number of years.

The dots are applied to the tops of specimen jars and to the outside of boxes containing jars from each individual project. In addition, large brightly colored dots are used for emphasis in situations where gelatinous specimens, such as many of the cnidarians and other planktonic organisms, have to remain in 5% formalin for long-term storage. In the latter case, this instruction also should be written on the top of the lid (Fig. 1).

The color coding key is clearly written in large type on cards that can be encapsulated in polyester film for added protection. Several cards are attached to the shelving to insure the understanding of the system by current and future collections management staff and researchers. All these dots are removable and hence when reusing the lids, the dots can be peeled off and the adhesive residue and remaining clear resin easily removed with a solvent.

Regular paper dots can be used but the colors often bleed when splashed with alcohol or water. In addition, some dot colors fade over time, especially if exposed to bright light.

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