Random Bits of Projects

November 3, 2008

Have a crustacean (crayfish) molt? You can set it and keep it!

Last update: April 24, 2010, Reader ideas added towards the end. Yay!

My crayfish recently molted successfully. If your crayfish has been established and is healthy, it is OK to take out his molt sometimes. Usually it is best to leave it in for a day or so and let the crayfish eat it (if he bothers) to get the materials back in his system. If you remove this one, let him have the next one.

Here is something to do with that molt should you like this sort of thing–set the molt!

If the molt has not been sitting around getting gross or nibbled on, remove it gently from the water using your hand or a small net. They are fragile so do not squeeze or swish it around too much.

Do this when you have time. Once it starts to dry, you cannot move the parts around. Also, lets hope your crayfish does not decide to molt when you have had too much coffee on an empty stomach. This is not the best set I have ever done. I was jittery and impatient. But I had to finish it before it dried.

The picture above shows a molt in the foreground and the crayfish recovering in the background.


  • Intact crayfish molt (clean with no flesh left)
  • toothpick or something similar to work in a small place. Here I used an old pokey thing you use to hold legs together when roasting a chicken. I forget what they are called. I am not much of a cook. 😉
  • paper towels
  • safe location for it to dry away from pets and other sources of damage
  • protective spray (optional)
  • WD-40 oil (optional)


Fold a paper towel and lay the molt onto it.

Get the crayfish molt to sit on its ventral (belly) side with the legs out on their correct side (none folded over under the belly, 5 on each side).

The picture above shows the molt laid out on its side.The back is up, exposing the gill area. The picture below shows the back up from behind. You can see right inside. This part needs to be pushed back down. The picture below, right shows the leg positioning by using a narrow device such as a toothpick.

Push the back of the crayfish down into place. This is where the crayfish backs out of its shell. Reminds me of an open hood of a car. 😉 The white stuff under the “hood” is where the gills are located.

Position the tail into a more natural position up against the back rather than laying flat. There should not be a gap between the tail and the back. Take a pinch of paper towel and roll it tight until it is the right thickness to place under the tail to keep the shape you want. Use bits of twisted paper towel throughout to position the body parts. You can try cotton or something else as well. I like the towels because I can keep tearing off what I need until I get what I want. It is also possible to make wedges as well.

Spread the tail fins if you wish.

Use a toothpick or similar item to move the legs to where you want. This part is tedious because they will want to fold back. I try to hook the feet into the paper towel that it is sitting on. I then wedge paper towel bits between the legs to help hold them. You may need to place another piece along the side to keep the animal from looking like it is about to tip.

If you want him sitting up a bit, place one under the front. Do not forget the little “arms” by the mouth and position those.

The claws will need several bits of paper towel, especially if you wish to have them raised. Use the toothpick to open the claws if you wish. You may need to stuff towel between the claws to get them open.

Wad a large piece of towel to place in front of the animal. Tease apart the 4 antennae. The two long ones can be placed on the large piece.

Keep adding paper towel bits to prop the animal how you would like it to stay. Once it dries, that is the way it will stay. Be careful on claw positioning so the animal does not tip forward when the towels are removed.

Let it sit out in a well ventilated area so it does not mold. Be sure it will not get bumped and broken.

You can spray a protective coating to prolong the life of the animal once it is dry. They do tend to lose color over time though regardless. You may wish to experiment with WD-40 to prolong color and life before adding a protective coating. This helps prevent the shell from getting even more brittle from drying out. It is limited and you may want to spread the oil with a cotton swab to prevent flooding it.  I used to do this years ago and I forgot how well it worked over time. I think I remember it doing pretty good. Polyurethane may cause the animal to turn red so you may want to try alternatives. I would love any suggestions. I tend to just leave the coating off these days after I add some oil (if any). So far my blue molts do turn more white over time.

You may want to keep it in a clear container for protection. These are fragile but very neat. Good for show and education. I prefer to keep mine this way.

This works on most crustaceans. I have also set crabs and lobsters this way for people. You can get creative with poses, but work fast.

If the molt you have found smells, I suggest not keeping it. Likely there is still tissue inside from a bad molt or predation (if you found it on a beach) and it will rot and stink horribly. Bad crustaceans stink! The final set molt should not smell at all.

Where did I get this idea? I just thought it would be neat to do one day and did it. I am sure others have done something similar. Or maybe I am just strange. Don’t answer that!


Here (above) is one picture of the finished molt set from above. I hope to have a few more pictures soon along with any old molts I can find that I still have.

The post about my live, blue crayfish is located at https://virtuallyamy.wordpress.com/2008/09/04/crayfish-as-pets-my-electric-blue-boy/

I also have a knitted crayfish at https://virtuallyamy.wordpress.com/2008/09/30/knitting-blue-crayfish/

crayfish-set-up-with-foilHere I am setting up a new one. He did not want to eat this one so I decided to give it a try. I am experimenting with having the weighty claws up in the air. I am not sure how well this will work. I will post an update showing the results. Here, in addition to wadded paper towels (good for pulling out some moisture), I also used aluminum foil I wadded into support structures for the pinchers. This turned out to be handy to mold the foil in a way to hold stubborn limbs that do not want to stay or to hold heavy ones up hight that the paper was not up to. It is currently drying for a few days as I type this.

crayfish-set-up-with-foil-frontIn these two pictures (left and right) the molt is about buried in support material. I will be amazed if it is not overbalanced when finished but I had to experiment.

After forgetting about the molt sitting around, I finally took a picture of the final product. I forgot to spray with oil when it dried so it is looking a little rough as far as color. It also got bumped, breaking an antenna off. But the main point of doing this one worked out. The claws stay up fine without tipping the molt over. The pictures are not great, sorry about that. But at least you can see enough to maybe give you ideas for your own. 🙂

Here is a message from a reader, Julie, who did this with a bamboo shrimp:

“I recently tried this with my Bamboo shrimp’s molt. It’s been sitting around for a month now (I really need to find a case for it). I used your method, but I also sprayed it with Krylon brand matte finish. It’s usually used for stuff like charcoal drawings but can also be used on painted sculptures. Since coating it with this, I didn’t notice any heating up of the color– however, my shrimp is naturally orange. But the colors didn’t change at all from when it initially dried, so I think this coating works pretty well. I don’t know the longevity for sure, but it’s been a month and still looks the same. Here’s a photo of it (this molt is about 3 to 4 inches long):”

You can see this message in the comments as well.

Additionally, Anthony Mills mentioned putting a molt in resin for a neat paper weight. Also see the comments section for full details.

Thanks everyone!

big-crayfish-molt-set big-crayfish-molt-set-above


  1. I have been trying to save my blue crayfish carapace and have no problems drying it out in a good position. I am having problems with what to coat it with. Polyurethane and clear nail polish seem to “heat it up” and it turns from a bright blue to pink. I noticed you mentioned WD040; won’t tha make it greasy and hard to put a coat over? What do you use for a protective coating?

    Comment by Judy Palomba — January 5, 2009 @ 7:05 am | Reply

    • Hi! Nail polish does not work too great, I agree. I have had some luck with polyurethane but it often does ruin the color. Actually W-D40 works well. You do not want to soak it but it does absorb. I have a few that I did not treat with anything and they seem to be doing well. The color did fade though. I keep these in a “display” container. Containers for displaying baseballs are good as well as some of those big, square plastic containers that colored paper clips often come in. I will try to post a picture of those. But it helps keep them clean, and safe and makes a neat display.
      So far I have not found the perfect preservative. I need to take the time and experiment more when I get more molts. It has been years since the last lobster molt I did where I had more products available to try on them.
      Do send a picture of yours! I would love to post it with due credit. 🙂 Keep me updated too! I do not know many crustacean enthusiasts. When the holiday settles I will try to find some old preserved lobsters and post pictures. Hopefully they survived my last move. Yikes.

      Comment by virtuallyamy — January 5, 2009 @ 10:06 am | Reply

  2. Hi!
    I am a science teacher and we are lucky enough to be working with crayfish. We have only one molt that we have been aware of. I positioned it and let it dry out. You mention polyurethane, care to give it a brand name and suggestions as to where I could buy it. How about application? Where do you set it so it doesn’t get stuck to whatever surface it is on while spraying? Do you have any idea if polyurethane works on insects too? I’d appreciate any help I can get. Thanks!

    Comment by whisperer — January 18, 2009 @ 9:19 pm | Reply

    • HI!
      You can go without polyurethane or Wd-40. I have one sitting out without either. It just loses its color. Try to find a clear container to keep it in so the dust stays off and it can be handled easier by students. Craft shops or hobby shops have display boxes but you can find all sorts of things to use. I have one in a clear box that colorful paperclips came in. Go to office depot and see the ones I am talking about (sorry, brand was thrown away). I need to add this to the post. I am behind on updates.
      I will get back with you on polyurethane ideas but you can to go Home Depot or Lowes for it. Set the critter on paper or something you do not mind getting sprayed and spray it while it is outside. Be sure it is dry before spraying.
      I will reply to your other posting soon through email as it will likely be long. 🙂 Give me a day or two.

      Comment by virtuallyamy — January 18, 2009 @ 10:20 pm | Reply

  3. Hi there, I’m looking to preserve Crayfish tails and wonder if anyone could tell me whether or not it is possible to add a certain solution to them to keep them malleable?? Or would my only option be to use them once dried and crustified??
    Any ideas most welcome! Cheers!

    Comment by Anonymous — January 24, 2009 @ 7:15 pm | Reply

    • HI, I am not sure on that one. I tend to deal with the live parts. Try emailing a university or a biological supply place. 🙂

      Comment by virtuallyamy — January 26, 2009 @ 12:54 pm | Reply

  4. hey!
    i own 2 crayfish and i was wondering how big they have to be before this project works…because mine are small, and i have tried to do this before…but, well…they were to small 🙂

    Comment by jessi — May 5, 2009 @ 11:44 am | Reply

    • I think about any size should work. The smaller ones are thinner and more delicate so they may be more difficult. If you have clunky hands like mine, they can just be frustrating. But keep trying! 🙂

      Comment by virtuallyamy — May 5, 2009 @ 2:10 pm | Reply

  5. Hi, my name is shandy and i have 3 crawfish one of them looks like hes turning blue, his claws and his body is to. i have a about a 10 gallon tank and they are all in there becasue they were attacking the fish thats in the other fish tank i just put them in there and they seem to be doing fine i just wanted to know if i should take the male out and leave the two females in or what i should do, i dont want them to eat each other they are too cool to watch. Also do you know how to tell how old they are? Because one of the crawfish had molted once i dont know if they are grown up or not, one of the females looks to small to be mature yet..okay ill stop blabin..oh by the way your crawfish is awsome, i want one like that..you know where i can get one that looks like that?

    Comment by shandy — December 7, 2009 @ 9:45 am | Reply

    • Hey there!
      With 3 in a 10 gallon, be sure there are plenty of tight places they can hide. One crayfish at a time should be able to fit in these spots so the one inside can better defend itself. A molted one is very vulnerable to getting eaten. If it cannot find a place to bury itself or hide well, you might consider putting it in a temporary tank until it hardens its exoskeleton.
      I am not sure if you need to divide the sexes. I would watch for any that get overly aggressive and remove that one.
      I often see blue crayfish in small petshops, not the big chain shops (at least here) but that is around here. They may be more popular in some areas, like Florida, than others. Not sure where to suggest. You might want to go into a small local petshop that has fish and ask if they can either order any or if they know where you can get them.

      Comment by virtuallyamy — December 7, 2009 @ 11:53 am | Reply

  6. A few moults ago, I built a wooden frame atop a sheet of glass. Put my shell in the middle and filled with surf board resin, turning it into a solid transparent light blue block with the shell in the middle. Took it to work and use it as a paper weight on my desk, its always a conversation starter with coworkers!

    Comment by Anthony Mills — April 20, 2010 @ 8:33 pm | Reply

    • Wow! Very neat!!! I might have to try this! Did you have any trouble with bubbles forming?

      Comment by virtuallyamy — April 21, 2010 @ 8:16 am | Reply

  7. I recently tried this with my Bamboo shrimp’s molt. It’s been sitting around for a month now (I really need to find a case for it). I used your method, but I also sprayed it with Krylon brand matte finish. It’s usually used for stuff like charcoal drawings but can also be used on painted sculptures. Since coating it with this, I didn’t notice any heating up of the color– however, my shrimp is naturally orange. But the colors didn’t change at all from when it initially dried, so I think this coating works pretty well. I don’t know the longevity for sure, but it’s been a month and still looks the same. Here’s a photo of it (this molt is about 3 to 4 inches long):

    Comment by Julie — April 24, 2010 @ 2:15 am | Reply

    • That looks great! Thanks for sharing. I will give that a try and see how it works on the blue. I am going to make note of this in the main body with credit to you. Again, Thanks!

      Comment by virtuallyamy — April 24, 2010 @ 6:12 pm | Reply

      • Cool, thanks for adding it to the article! As of now, the color is still almost totally intact, although it is probably not as bright red around some of the corners as it used to be. However, I haven’t put it in a case or tried to preserve it (other than the matte finish). If you ever end up trying it on a blue one, I’d be curious to see if it’d work for that color 🙂 Thanks again.

        Comment by Julie — June 13, 2010 @ 1:52 am | Reply

        • Thanks for the update! 😀
          If I do try this in the future, I will let you know. I would like to, I just have so much going on right now. Ack!

          Comment by virtuallyamy — June 13, 2010 @ 11:16 am | Reply

  8. Hi my son has a crawfish…it went through the molting process but still does not move. its been about 3 weeks now. when I feed him he moves his mouth and back legs but nothing else. is he sick? what can I do?

    Comment by Christina — May 31, 2010 @ 8:27 am | Reply

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