Erosion Taxidermy

Re: Slip molding (erosion molding)

I would be happy to give you some pointers. What is it you want to know?

 

Re: Slip molding (erosion molding)

I'll send you a PM with my contact info. There's a lot to go over, and it will save the folks on here from a long back and forth. It will be much easier to cover in a phone call. But, please document your process if you make an attempt and share it here when you're done so others can benefit too.

Talk to you soon,

Alicia

 

Re: Slip molding (erosion molding)

Hi Michael,

I decided to post my response to you here as well since it's hard to find information on the process.
Erosion molding/slip casting

So, there are many ways to do this. The basic concept is that the subject is coated in a medium that captures the pelage, plumage, scales, hairs, etc. down to the surface of the skin, and all of the material not captured is allowed to rot away until completely removed. The hollow of the mold is washed thoroughly, and another medium is cast into it. The roots of the fur, feathers, hair, etc., that were once embedded in skin, are exposed inside the mold now that the skin has been rotted away. When the casting medium is poured into the mold, it grabs the exposed roots. The outer coating/mold, is then melted/dissolved/removed, leaving a perfect cast of the subject. The end result is a form of the animal, with every hair/feather in place as it was in life. It will resemble taxidermy, but it is far from it because the only material that remains is the hair/feathers and the medium that they are captured in. In theory (with lots of practice) this method can produce a result that is more accurate than taxidermy or freezedrying can ever produce, because it removes the variable of human error as far as anatomical accuracy goes. It also beautifully replaces the skin, which can be achieved with remarkably life-like results by using a flesh toned casting medium with the appropriate level of translucency. Take this rat specimen prepared by UK taxidermist Emily Mayer for example, she has mastered this technique.
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There is no skin there, it's just a hunk of plastic with fur stuck in it. Amazing huh? Look at the exposed "skin" on the ears, feet, and tail. They all have a lifelike fleshy appearance, with some translucency, and every hair is placed where it should be, even the "peach-fuzz". With a taxidermy mount or freezedried specimen, the skin would be discolored and have to be painted, which takes away from the waxy translucent look of the skin and paint is hard to keep off the fur. So we begin to see where this method has its superior qualities.

Now, for the choice in mediums and methods to use... so many possibilities! Here are the rules: The mold medium should be something that is reversible that will not harm the fur or feathers it coats. The casting medium (what is poured into the mold) should be durable and not dissolved or weakened by the same means of removing the mold, and has to be a material that does not bond to the molding material. For example, you could not use a wax, moulage, or hot glue mold with a wax cast, as the cast would melt when the mold was removed by heating. Another example is that a resin mold could not be used with a resin cast, because they would bond together, and so on.

Another thing to consider is that since the casting medium is replacing skin, it should be a material that you can tint or color to match the skin color of the subject, as well as control translucency (if necessary). This is especially important in subjects that have sparse hair or feathers and a lot of exposed skin. A combination I have had great success with, and a good combo to start with as a beginner, is a wax mold and resin cast. I most recently used this combination to slip cast a turkey vulture head, which I will use as my case example. As I mentioned before, animals that have sparse pelage or plumage, or a lot of exposed skin are the ones where this technique comes in most handy. A vulturine guineafowl, a chimpanzee face, a newborn raccoon, and my turkey vulture all make excellent candidates.

To prepare my turkey vulture head, I began by making an incision just above the feather line on the neck, and severing it from the body. I then injected the eyeballs with enough water to plump them up to where they would be in life, using a tiny insulin syringe (28 or 30g needle) so they would not leak. I impaled the neck and head on a long nail driven through a small wooden board to hold it in place and popped it in the freezer. Then, like preparing a specimen for freezedrying, I monitored its position throughout the freezing process by checking on it every 30 minutes or so and adjusting it as needed until frozen solid in the position I was happy with. Once frozen solid, I removed the head from the freezer and dipped it in melted paraffin wax. In this case, I chose paraffin because of its low melting point so that it would not defrost the skin enough to droop out of place before the wax hardened. For larger thicker skinned animals, I prefer bees wax or another material for durability's sake. I continued brushing and pouring wax over the head until there was at least a 1/4 inch layer covering it. Then, I floated the head on its board in a bucket of water and let it macerate (I let bacteria do the work). Over the next two weeks, I checked in on the head daily and gently removed what I could by hand. After a day, I was able to pull the head off the nail and board easily. After a week, the flesh had begun to liquefy just like macerating a skull. I rinsed it out and carefully pulled out the softened tissue and vertebrae as they came loose, taking care not to scratch the inside of the wax mold. I would always rinse the head in very cold water before working on it to ensure the wax was stiff enough that I wouldn't warp the shape by handling it. Eventually, all of the flesh was rotted away (I should mention this phase is very smelly work!), leaving just the bones of the skull rattling around inside the mold. I carefully cut the skull up with surgical scissors, and removed it bit by bit with forceps through the opening at the base of the neck, and again being very careful to not gouge the wax mold in the process. The beak sheath slipped off the skull with ease, and remained in the mold which ended up looking great in the end.

Once all of the skull and surrounding tissue were removed, I gently washed the inside of the mold with soapy water to clean the smell and residue away as much as possible. I then rinsed it well (again, in cold water) and left it to dry for a day. When dry, I carefully placed warmed glass eyes in the mold (dipped in near boiling water for a few seconds so that the wax would melt just enough on contact to grab the eyes and hold them in place) where the impressions from the real ones lay, and poured a tinted urethane into the mold. Before the urethane kicked, I floated a bent wire in it that I would later use to attach the head to the taxidermy body. I let the cast sit until the next day to ensure it was fully cured, and dropped the whole thing into a pot of hot water. The majority of the wax melted away, and I pulled it out to reveal my cast vulture head with all the tiny fuzzy feathers embedded in the urethane and looking awesome. I used a paint brush and a heat gun on a low setting to melt away the remaining paraffin. At this point, there was still a bit of residual smell, so I scrubbed it gently and quickly with a soft toothbrush and a 10% bleach solution and rinsed it really well in cool water. The head was now finished and ready to go!


In summary, this is a really interesting approach to replicating a specimen. The methods and materials used are limited only by your imagination, and with testing and practice will produce a beautiful end product. Best of luck with your experiments, and let me know if you have any questions along the way.

Have fun!

Alicia

 

Re: Slip molding (erosion molding)

Thank you AliciaG, and crowkiller for bringing this up. Quite informative.

 

Totally cool AliciaG, do you know what was used to make the mold of the rat?

~S

 

Incredible post, thank you. When doing this on something like a mouse, does the waxed body need to be cut open for the maceration, and if so where is best? My guess would be near the head to facilitate eye replacement?

 

We used Plaster of Paris for molding turkey heads and allow 3 to 5 days in the mold for feathers to slip. After the mold had the head removed and was rinsed, we would pour Chicago 501 casting latex into the mold, once the latex had dried the head can be removed. The fine hairs and feathers remain in the casting.

 

Newborn elephant calf from National museum of Scotland, made with same technique.

 

Fascinating, Alicia!
Thanks so much for taking the time to share your expertise.
I CANNOT IMAGINE that elephant calf being made with this technique!... talk about STANK!... LOL

 

X2! And EM, thanks for sharing the elephant pic too.
Best, Scott

 

I've been trying to research this technique and not come across many results. I know it's an old conversation but hoping someone can still point me in the right direction with a question I have... When dealing with feathers and fur, how do you make sure than the moulding medium has penetrated to the skin?
I've tried a low melting point soy wax, but have encountered issues with it not going going deep enough.
And how on earth do you get beeswax out of fur successfully? It is absolutely doing my head in!! Lol
Does plaster of Paris come out relatively easily?

 

Use condensation cure silicon rubber. The type you use for moulding antlers etc. work it into the fur with a brush. Let it cure and follow the same process as above. When you’re ready to remove the silicon from the fur , soak with white spirit (mineral spirits)and it will break down the silicon rubber and can easily be removed from the fur.

 

thank you, but what if one is working with feathers (which could be damaged by trying to work silicone into them) or wants to use silicone as the casting medium, such as was done with Emily Mayer's subjects?

 

Matuska has a video on erosion mounding a competition turkey head by a world class taxidermist.