Scale mold help!

[MerCat]

So, I'm working on making a full silicone tail and I'm still trying to decide the best way to make my scale mold. I've made a mold box already, and I've laid tons upon tons of foam scales. I know the next step is using the shell-shock to create the hard plastic mold but I'm trying to come up with a way to best seal the scales to make sure that the liquid plastic doesn't absorb into the foam scales. I've seen people use vaseline (more for latex though, right? I'm not sure how vaseline and silicone will mix?) and i've seen people cover the foam with clay and seal off all the cracks and what not. Two problems, 1)i'm not making a latex tail, and 2)I don't have clay and I have a pretty big scale sheet to put clay all over if I did have it.

So, here's what I was thinking. My brother suggsted that we spray a layer of clear coat over the foam scales to make them impenetrable to the liquid plastic. Has anyone done this? Also, I've heard of a Clear acrylic spray. The only thing is, I'm not sure how the liquid plastic will react to the chemicals in the clear coat or clear acrylic spray.

Any ideas? Suggestions? They would be greatly appreciated! (My foam scales are on a wood board, I know that liquid plastic and wood don't agree with eachother, so I have to find some way to protect the wood from the liquid plastic.)

[Jessica]

Hi Mercat

I'm just a step ahead..well a disaster ahead of you. Im making a silicone tail and used foam circles layered on posterboard for my mold. I used shell shock with the manns 200 mold release and it was a disaster!! The shell shock is tough to work with( it thickens very quickly and I used the slow version). The foam scales absorbed the shell shock and the shell shock went in between the cracks. My scale mold is 52" by 24" and I've been scraping and picking out bits of foam and shell shock from places it doesn't need to be for hours already.


When I talked to smooth on they had recommended using krypton lacquer to make a barrier. I did a test sample of this and it was a disaster so I don't recommend it. The foam absorbs the lacquer and it made the shell shock stick even worse than before.

I can't afford to start over so I'm going to try to fix the mess that I have, but if I were you I would use clay. I made the sides of my mold box from monster makers clay and the shell shock came right off!!! Monster makers clay can be melted in the oven or microwave and I would melt it and spread a layer on top of the entire sheet of foam scales and the wood of your mold box. I think it's about $35 for a 5 lb container but it can be reused so its absolutely worth it. It also works great for sculpting a fluke.

Here's my sheet before and my mold after:

[MerCat]

oh no!!! I'm so sorry that happened to you! And thank you so much for the heads up! Wow I would have been in for a major disaster!

so you think that heating up clay and putting a layer over the scales is the best thing to do? I guess I will have to try this and just spend the time molding the clay around the foam scales....whew it'll take time, but the outcome will hopefully be worth it!!

[Jessica]

Just make sure the clay you use is ok to be heated and is sulfur free. Silicone won't cure in the presence of sulfur. I don't know if shell shock is the same way but I'm not taking any chances! You can use any clay that is sulfur free, but if you find one you can melt it would save some time.

good luck!!

[Mermaid Lorelei]

Even if shell shock doesn't need sulphur free clay, it doesn't matter. Since silicone is going into the shell shock mold later, you can't use clay with sulphur. The slightest traces will keep the silicone from curing.

[jazz2453]

Mercat, I actually just contacted Smooth-on asking your same question. I'm still waiting for an answer but I'll you know if they say anything useful. It makes me sad to see what happened to Jessica:( That's why I'm trying to find as many answers as possible.

[emma11]

Idk about well shell shock, I've never used that, but I just made my plaster mold successfully. The only release agent I used was actually WD40, worked like a charm, and it's something I had around the house. Not sure if it would work with Shell Shock, but you could make up a tiny version of the mold to see if it works!

[jazz2453]

I just read your thread. Your tail progress is looking great so far!:) What type of plaster did you use? And do you know if it would work for a silicone tail?

[emma11]

(wow late sorry), I just used plaster of paris, i had a ton of that left over from some previous projects. The stuff takes a long time to dry, but it gets detail like nothing I've ever seen. Other than perhaps alginate. It's been... a while of waiting for it to dry. As in, I molded maybe a week ago and it's still drying. But once it's dry, it's impossible to scratch. As far as I know, this will work just fine for a silicone tail! Plaster won't mess with silicone once it's bone dry, and you should be able to get as many pulls from it as ultracel 30 or shell shock. Both of those are slower drying materials from what I've read. Plaster of paris was a mad dash to completion, haha.

[MerCat]

Thank you everyone! All of your answers have been extremely helpful.

[Firemaid]

POLYURETHANE!!!!
It will not stick to your foam.
It's cheap.
It's lightweight.

[MerCat]

Firemaid, and silicone will still cure if it comes in contact with polyurethane? I just haven't done much research i guess on it. Any particular type or is it all one kind?

[MermaidHyli]

Ive really fallen in love with fiberglass. It Iis toxic however so you need to to the correct safety procautions. The best place I've found to get fiberglass matting and resign is from us composites and really isnt that expensive.

[MerCat]

I've read a little on the process with fiberglass and the resin and matting and it just sounds all so complicated to me. Is it hard to use?

[MermaidHyli]

Not at all! Basically you have to layer the fiberglass one sheet at a time and dab the resin/catalyst solution onto the matt as you go making sure no bubbles are in it. If you want a smooth coat you can gel coat it but for foam I wouldnt recommend it. Make sure to mix the resign with proper ratios like 1 oz=10 drops of catalyst. And mix in a.gladd jar preferable. Ive melt so many plastic cups and sometimes to my hand ouch haha be sure to wear long sleeves and pants that you dont want to wear again and nitryl (sp?) Gloves. If you are doing any sanding you should have a resperator. Hope this helped :)

[Jinx]

$20 fix. I had the same problem. I even used vasoline but it took the details out. Then it fell apart. My friend took a mask making classes and we figured out the solution. Pam cooking spray, linen, and cement all. Once your scales are loaded make a frame out of 2x4s and spray 2 to 3 coats of Pam all over it. Then I used cement all to make the mold so I can us see it forever. Mix it on the thin side with slightly more water thanthey suggest. Use a natural fiber stiff brush and brush some onto the scales a thin layer at a time being sure to not have bubbles. It helps to have someone mixing the cement all while you put it into the mold. Then cut strips of the cotton or linen in every other layer. I made the mold about 1 inch thick. Then the best part is cement all is made for castings so in about and hour from your last pour of cement you then take the 2x4s off place another board on top and flip it over. Have a helper for that too as it is quite heavy for a 2 ft x 4 ft mold. Once flipped gently and slowly pull the foam scale sheet off. Then you have a solid permanent cement mold for your scales.

[MermaidLychee]

$20 fix. I had the same problem. I even used vasoline but it took the details out. Then it fell apart. My friend took a mask making classes and we figured out the solution. Pam cooking spray, linen, and cement all. Once your scales are loaded make a frame out of 2x4s and spray 2 to 3 coats of Pam all over it. Then I used cement all to make the mold so I can us see it forever. Mix it on the thin side with slightly more water thanthey suggest. Use a natural fiber stiff brush and brush some onto the scales a thin layer at a time being sure to not have bubbles. It helps to have someone mixing the cement all while you put it into the mold. Then cut strips of the cotton or linen in every other layer. I made the mold about 1 inch thick. Then the best part is cement all is made for castings so in about and hour from your last pour of cement you then take the 2x4s off place another board on top and flip it over. Have a helper for that too as it is quite heavy for a 2 ft x 4 ft mold. Once flipped gently and slowly pull the foam scale sheet off. Then you have a solid permanent cement mold for your scales.
Six months later, but I wanna drop a big THANK YOU for this information; I can't have ShellShock or anything similar out in the humidity of Hawaii, so this information is the bees knees. Plaster of Paris or this are my only options, it's nice to have more than one. :3

[Jinx]

Six months later, but I wanna drop a big THANK YOU for this information; I can't have ShellShock or anything similar out in the humidity of Hawaii, so this information is the bees knees. Plaster of Paris or this are my only options, it's nice to have more than one. :3

No problem glad I can help

[Aziara]

$20 fix. I had the same problem. I even used vasoline but it took the details out. Then it fell apart. My friend took a mask making classes and we figured out the solution. Pam cooking spray, linen, and cement all. Once your scales are loaded make a frame out of 2x4s and spray 2 to 3 coats of Pam all over it. Then I used cement all to make the mold so I can us see it forever. Mix it on the thin side with slightly more water thanthey suggest. Use a natural fiber stiff brush and brush some onto the scales a thin layer at a time being sure to not have bubbles. It helps to have someone mixing the cement all while you put it into the mold. Then cut strips of the cotton or linen in every other layer. I made the mold about 1 inch thick. Then the best part is cement all is made for castings so in about and hour from your last pour of cement you then take the 2x4s off place another board on top and flip it over. Have a helper for that too as it is quite heavy for a 2 ft x 4 ft mold. Once flipped gently and slowly pull the foam scale sheet off. Then you have a solid permanent cement mold for your scales.

Whoa! I never even thought of cement. High humidity is a problem where I live too. And cement is so much cheaper than resin! Any idea if this would work for a clay scale sheet and my fluke sculpture? I'm using plasticine clay, if that is relevant.

[Aziara]

GAH! I just realized you meant the stuff to repair cement cracks, not cement itself. Glad I saw that or I might have gone out and bought normal cement, lol!