Preserving Specimens

It’s me again, the “bone collecting” teacher with a new question. How effective is rubbing alcohol in preserving specimens? Since I live at the beach, I am always finding marine specimens to use for student observations. Typically, I do not have any biological preservative available, so I’ve been using rubbing alcohol.
—Susan, Myrtle Beach, South Carolina

Many of us remember high school or college biology labs full of jars with preserved specimens and labels showing the name and when it was collected. They were interesting to look at, but the formaldehyde or formalin frequently used as a preservative in those days is a substance to be avoided today. In the NSTA Press book, Inquiring Safely, “Formaldehyde solution—also called formalin—has been replaced largely by newer, less odorous, and less toxic preservatives with a variety of trade names. However, most still contain formaldehyde, albeit in lesser concentrations and mixed with other ingredients. Treat all specimen preservatives as though they contain formaldehyde, particularly if you or your students are sensitive to materials of this type.” (p. 72)

In terms of alcohol as a preservative, I saw conflicting advice on the websites I examined. I contacted a friend of mine, Dr. Walter Meshaka, a zoologist and the senior curator of the section of Zoology and Botany of the State Museum of Pennsylvania. Here is his response to your question:

I advise strongly against formalin. You can use the standard 40% Isopropyl; however, a better choice, also to be found in most drugstores is ethyl alcohol. Additives keep it from being drinkable, so it is not ethanol [that is, it is] not white lightening. If available as stock (c.a. 95% or so strength) then dilute to about 70-75% and you’re good to go!

Whether you choose isopropyl or ethyl alcohol, be sure you have the appropriate Material Safety Data Sheet on file and use the appropriate safety procedures as you work with it (e.g., goggles and ventilation). Be sure the jars are securely sealed so inquiring fingers are discouraged from opening the jars.

I’ll put in a plug for specimens preserved in blocks of acrylic. Although they can be expensive to purchase, they last for many years and the students can handle them without worrying about breaking a jar.

For beachcombers, be aware of any regulations or required permits for specimen collecting. Some wildlife refuges or other parks and private beaches may have restrictions on taking things away from the beach.

As teachers, we all have collections of stories and anecdotes from our classes. In addition to her question, Susan and one of her students share a related story:

Things You Should Always Ask Your Students

During our study of animals, my sixth-grade students often bring in specimens to identify using our field guides. Shortly after Thanksgiving, Franklin brought in a jar containing a snake his father had killed in their yard. Since the snake had not been placed in a preservative, I suggested that we open the jar to add rubbing alcohol so we could include the specimen to our collection for observation. I had preserved specimens in the past using this method so was not concerned.

He and I opened the jar, and I immediately learned something you should always ask your students. The odor from the jar almost knocked us off our feet. The odor cleared every student out of my classroom, diffused down the 50-yard hallway (causing other teachers to rush out of their rooms), and finally made it to the principal’s office.

After reassuring the administration, teachers, and students that is was simply a matter of a stinky science classroom, everyone settled down. I expressed to Franklin my surprise about the overwhelming odor. Looking perplexed, he said, “Well, the snake has been dead since Halloween.”

So I learned one thing you should always ask your students: Just how long has the specimen been dead?

This entry was posted in Ms. Mentor and tagged , . Bookmark the permalink. Both comments and trackbacks are currently closed.


  1. invisible
    Posted November 29, 2011 at 1:56 am | Permalink

    Thank you for the advice on the proper way to preserve a specimen of plant material ! I’ve been racking my brain !!!!

  2. ricardo
    Posted December 15, 2012 at 3:39 pm | Permalink

    i used the same steps as requested but my ginea pig that passed bloated and looks brused is that normal

  3. Allison T
    Posted March 14, 2013 at 5:34 pm | Permalink

    If the specimen I am interested in preserving is just a bone, does preserving it in alcohol work in that case as well?

  4. Angela
    Posted April 24, 2013 at 12:58 pm | Permalink

    Can I preserve in a plastic bottle, so I can safely pass the specimen amongst student hands?

  5. Mary B
    Posted April 24, 2013 at 5:21 pm | Permalink

    Angela — In addition to the specimen, what else is in the bottle? I would not use formalin or any other formaldehyde substance with students. If it’s an alcohol solution as Dr. Meshaka in the blog suggested, you should be sure that the bottle is completely sealed so that it cannot be opened by “curious” students.

  6. Erika
    Posted October 16, 2013 at 3:59 pm | Permalink

    One more thing about preserving in alcohol (or any other liquid preservative for that matter) that you might want to add: for larger specimens (like guinea pigs, or large shrews), you’ll need to either inject the fluid in one or more places, make small incisions to let the fluid in, or pour the fluid down the throat (for smaller “larger” specimens). If you don’t, you’ll likely notice bloating/floating, which means the insides are rotting because the preservative didn’t penetrate all the tissue. This was likely the case with Ricardo’s guinea pig. 🙁 Once the tissue starts decomposing, the specimens most likely can’t be saved, especially once it starts bloating.
    Other than that, great article! I remember my fifth-grade science teacher letting us dissect crawfish that had been preserved in formaldehyde (and this was only a few years ago!). At least now I know that once my 9th (or, more likely, 10th) grade science class gets to dissections, the specimens are more likely to be preserved in alcohol. I’m hoping I can take one home (though regulations may not let me)! XD

  7. Sophia
    Posted January 27, 2015 at 2:27 pm | Permalink

    I find the specimen preserved in jars to be highly offensive to be on display anywhere (especially in high school classrooms). After doing some research these animals did not die of natural causes, and they were killed for no scientific or human benefit. They were killed for high school students to gawk at. We become calloused to the fact they were killed for the sole purpose of staring at. This is wrong, unethical, inhuman, and dare I say evil. We can not kill animals to put them on display.

  8. sally
    Posted February 4, 2015 at 12:37 pm | Permalink

    Enjoyed your blog – thank you! Have a weird question for you. My daughter, who is 8, has always wanted to be a doctor due to an earlier injury when she was about two – we’ve been on many college road trips and she’s always know she wants to be a doctor and has toured at Harvard, Cornell, Stanford, Yale, etc. She’s been to them all and has a straight path ahead of her (she’s in third grade and doing 9th grade work). So shortly after she had her own injury, I rescued a Queensland Heeler off of an Amish farm in upstate NY (where he was left untreated for a year and close to death) – with an injury and had his foot mangled. For the last seven years we’ve been trying through a specialist and several surgeries to heal the injury. Now, we have found, through a new specialist, that did an MRI and found that the original injury had left dead bone and metal inside that has now been grown over and impossible to remove. In order to remove the cause of continuous bacterial infections, Sparky has to have the paw just above what we think of as a wrist amputated. Through all of this, and it has been a difficult road, my daughter has learned the patience of a saint to bandage him and take care of him, even through his worst pain he has been gentle and even joyful (and even saved our lives from a wall fire). My daughter would like to preserve his foot in a jar so she can have it in her doctor’s office and tell the story of Sparky – and how amid this pain over the years he still found joy and a determination to heal. An amputation is by no means a quick fix, as it has it’s own set of long term issues. He will be receiving a prosthetic made with a 3-D printer derived from the 3-D C.T scan. Anyhow, the long, long and the short of this question is — what on earth do we use for the preservative? Hair and bone — how do we save it in an apothecary jar? Not sure what “dilute” means, with water? Could sure use your advice 🙂 Thank you,

  9. Jannie
    Posted March 10, 2015 at 9:55 am | Permalink

    Hi~ I would like to ask if what formulation (70, 40 etc.) of isopropyl alcohol as well as ethanol is advisable to be used in preserving biological stains?

  10. Patrick
    Posted June 9, 2015 at 12:18 pm | Permalink
  11. Mary B
    Posted June 12, 2015 at 11:34 am | Permalink

    It seems to fit the description offered by the museum curator in the blog, but this is not my specialty. You could ask the pharmacist about this or ask a museum curator in your area about what would be the best preservative.

  12. Evelyn snow
    Posted June 23, 2015 at 6:21 pm | Permalink

    I haven’t workers with life science specimens in a couple of years, and this is not an advertisement, but at one time Carolina Biological had awesome materials and kits for dealing with specimens. They also provided great phone support for questions. It’s been a while, but it might be worth contacting them. They can probably provide support on the safe handling of the chemical you choose to use, and the shelf life of your process and the preserved specimin.

  13. Tammy
    Posted May 11, 2016 at 8:34 pm | Permalink

    So can I preserve a deer eye that I plan to dissect at a later date in ethyl alcohol and still take it out and dissect it at a later date?