We fill red-top tubes with the gel from cold packs, aspirate the air out with a needle and syringe, and freeze the tubes.
Then when we need to send samples that must be kept cold to outside laboratories, we pack a labeled frozen gel tube next to
the sample in a Styrofoam (Dow Chemical) mailer. The packages are lighter when we use these frozen gel tubes instead of frozen
gel packs, and our laboratories report that the samples are still cold when they arrive.
Amanda Barnett, veterinary assistant