Thursday, May 26, 2022

RESPONSES: Pulling over carver foam

Schafer, Kristin

Hello to all and thank for your many responses. Here they are:

I have been told and tried several techniques:

1. wet mold and wet stockinette

2. painting/coating the foam with a thin layer of plaster… followed by cellulose acetate sealer.

3. pva bag

4. using a separator like armour all to coat the stockinette with.

*adjustments to vacuum pulling also needs to happen but has never clearly been explained to me. For example… pull the plastic, get a good seal, then cut the vacuum off. The rationale is that the foam/porous mold will draw a stronger flow of vacuum when compared a plaster mold that gets its vacuum solely from the wick/stockinette or nylon. This goes against thermoforming principles that gary beddard preaches in his thermoforming lectures. Size of mainfold, duration of time plastic cool while under full/continuous vacuum (approximately 3x longer that required to heat the plastic)

I’ve never liked fabricating over foam prosthetic or orthotics… when we blistered check sockets of foam carving for prosthetics at Michigan we wet the nylon prior to the pull… then it was all plaster mods after the initial test socket. I hope that helps and I would really like to see the responses if you would share.

Nylon and straight water. No separator, no silicone spray, no soap.
Just a soaked nylon in water.
I cannot help with AFO’s, but we pull test sockets and flexible inner sockets on foam regularly.

This is our process for test sockets using Thermolyn Stiff or Vivak
– Take a 1/8″ rod and put a hole from distal end of model to the proximal end
– 4 layers of FeatherStretch nylons
– Soak with water within a few minutes of pulling plastic
– We also run our vacuum at 10 mmHg, otherwise the nylons embed in the plastic
– We also turn our oven down about 10 degrees for foam

This is what we have used after 2 years of trial and error, I would be interested to see other methods. We spent a good amount of time trying other methods we were told were full proof, I went to the extent of having a manufacturer come in and show us their method and it didn’t work for them either. The best I can tell you, play with oven temp and vacuum pressure more than what you do with the mold itself. All the silicone pastes and liquids just make a mess. We pull about 20 check sockets a week using this method and the only issues we run into, is when someone doesn’t turn the vacuum pressure down. Hope this is helpful.

Nurses Nylons over the foam and then spray with water right before you pull your plastic.

I’m sure 20 people already responded. Plus here are the answers when it was asked before. It’s super easy just need to see which method is best for you. Good luck.

We use one dry and one wet stockinette with silicone spray before the plastic is ready.

That’s for body jackets only, I would not use silicone on AFO’S, LPS silicone spray (# 01516) it water based and you can get it from Grainger. Be sure that you wring most of the water out of the stockinette.

Those were all I got. Thanks again everyone. You have been very helpful.


Kristin Schafer, B.Sc.(Kin), CP(c)
Certified Prosthetist
Health Sciences North
Rehabilitation Engineering
41 Ramsey Lake
Sudbury, ON
P3E 5J1
P: 705-523-7100 x3176
F: 705-523-7051

Health Sciences North’s vision is to be globally recognized for patient-centred innovation.
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