Can you use Plaster of Paris to make a mold?

[Mahi Mermaid]

I visited a local Smooth-On product distributor today and he was telling me some less expensive options for mold making that still work fine with the Dragonskin but was curious if any of you have tried what he suggested?

He said to cover the foam circles in Plaster of Paris (no sealant or release agent) then to spray release agent in the hardened POP mold and then add in the silicone.

Also he said for the fluke, that it didn't matter why type of clay (as long as it's sulfur free) it could be mold-making clay or clay that dries (which is what can be found most at craft stores) as long as a sealant is applied before the POP and then the release agent again in the POP mold before the silicone is poured in.

What do you guys think? My experience with POP is that it's pretty brittle and I can just see that huge scale mold getting broken into pieces. Also do you think that it will catch all the small details?

Also what do you think about sculpting the fluke with the drying clay vs. non drying clay? Do you think that would work?

Curious to see what you guys think!

[MerQueen Nerissa]

When I made my silicone tail, I used plaster of Paris for the molds, and it worked just fine. It does capture good detail, but be aware that there WILL be bubbles. It shouldn't be too fragile as long as you make it thick enough.

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[Anahita]

I think another downside to POP is that it's much heavier than the plastic molds. Some mers have good luck with it, some others have their molds break and so on.

I usually prefer non-drying clay for everything. It's reusable, so you get to make something else with it afterwards without having to buy more clay, and it has the benefit of being a material you can go back to and change later on if you decide you don't like something. With drying clay there's less room for error and time for changing your mind. And if you plan on making things in the future, you have to buy more of it.

[Mahi Mermaid]

This is great info! I just checked my test scales and the POP actually ended up under and in between the foam scales ( I guess I didn't glue them down enough) What type of glue do you use for the foam scales? I just used some Elmer's glue I had at the house. I'll post pictures soon!

[Mahi Mermaid]

Also what is the best product to use for the molds?

[Mermaid Momo]

I think most people put clay in between the scales, but I think E600 will work really good. Put it around the whole scale, close to the edge to close off any possible gaps.

[Triton-Mahtlinnie]

I used plaster of paris for all my molds when I made my tail. My fluke mold was a good 4 inches thick. For my scale mold, I reinforced the plaster with fiberglass cloth, which kept it strong but thin.

I like using Plastalina for clay, it doesn't dry and peels out of a plaster mold easily. With my foam scales, I put clay in especially large gaps to keep the plaster out, then coating the whole sheet in Shellac. The Shellac made them peel out fairly easily. I was working with latex, tho, I dunno if Shellac will do anything to silicone.

[Trident True]

I used POP for my molds but i bought a more higher quality POP. i do believe that there are better quality out there not to mention the hardness. in regards to molds breaking, it just comes down to common sense really. make the mold sides as thick as you can go without having to use excessive plaster. i made my fluke mold about 3cm thick as i was terried that it may snap in half, nope everything was all good. Before i poured my silicone in to my mold i used a fixative (spray you buy to spray over soft pastels) it was called crystal cote. as far as i know there is no silicone curing issues with POP. ALWAYS do test pieces first. as for clay i used maker monsters but any Plasticine clay will work fine, any any sulfur free clay as mentioned. POP will stick to foam so its best to use a realease agent. Vaseline will work fine just don't cake it on a thin layer should be enough. hope this helps

[Mahi Mermaid]

Thank you guys so much. I'm going to try and search for some fiberglass fibers today to reinforce my scale mold because I did another test that was about 2in thick and it still broke in half when I was demolding (I have my work on a tarp on a table) wondering if I need to have it in it's own separate box so that I can lift it up and pop it out when demolding instead?

Do you know where to get the fiberglass fibers? I only seem to be able to find the cloth---

Also would it be wise to get the foam that has the adhesive already on the back? I couldn't seem to get that sheet to fit through the hole punch---suggestions??

[Anahita]

Wal-mart and Home Depot both have the fibers and the cloth for fiberglass. I think Wal-mart might call it fiberglass matting? It'll be the fatter bundle.

Also, I've seen other mers use the pre-punched adhesive-backed foam circles and it's worked out fine. I think it's a bit more costly, but given how much time it saves, it seems like a better idea and investment, IMO.

[Mahi Mermaid]

Yes--That's what I planned to use first, but they wouldn't fit into the punch---they were too thick. I actually ended up getting foam from the dollar store (which is thinner than any of the sheets at Michaels) and am still having trouble.

The Martha Stewart punch snagged the bottom of all the circles (so I returned it)
The Fiscars didn't fit the foam (not even the thin foam)
and then there was one more, but they told me if I purchased it and it didn't fit, I wouldn't be able to return it because of the packaging (would have to be cut and couldn't be put back together "pretty") for resale.

So now I'm stuck!

[Triton-Mahtlinnie]

The fibreglass I used came in a big roll as a cloth sheet. I cut them up into little bitty strips and did several coats. (note: always wear gloves and cover your bare skin with fibreglass. it itches like crazy) The stuff is called "fibreglass veil"

[swimmingsammi95]

When I did my molds I used fiberglass resin and reinforced it with fiberglass cloth. You can buy it all at home Depot or Lowe's. I used petroleum jelly as a sealant/release agent and it worked very well and gave me a very strong mold. But when you use it, make sure you do it outside or in a well ventilated area like a garage and do it in small increments and layers so you have less risk of bubbles. Do a thin layer and let it cure, then another and another until you feel it is thick enough. The clay I used was a non drying clay and it was difficult to clean out my mold due to the fact that the resin heats up as it cures and the clay softens when it is heated. I did not lose any details in my sculpture though. I used foam for the scale sheet and had to do a lot of spray adhesive and weighing down. I never ended up using a mold for my scale sheet because THAT was a DISASTER. But resin is a good cheapie option.

[Mermaid Momo]

What's a really good POP brand?

[Mermaid Wesley]

You CAN, but yes it might break. I've seen them break a lot lately.


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[Mahi Mermaid]

Awesome info! I started with the POP from Michaels (comes in an 8lb bucket), but realized I would need a lot more so I'm going to home depot today to get the big 25lb bag...I think DAP is the brand and it's called "wall plaster" from the hardware stores. I'll let you know how it goes! ---Also going to ask about the fiberglass fibers but otherwise I did see the fiberglass cloth at Walmart today!

All finished with my scale sheet---like Jessica I'm going to do the body in sections since I didn't have much luck with cutting out the circles! I'll probably need 2 1/2 sheets each side since I want this tail to come up over my belly button :)

25946

[Trident True]

cool hope everything does to plan.

[Mermaid Kelda]

I've seen other mers use the pre-punched adhesive-backed foam circles and it's worked out fine. I think it's a bit more costly, but given how much time it saves, it seems like a better idea and investment, IMO.

Yes--That's what I planned to use first, but they wouldn't fit into the punch---they were too thick. I actually ended up getting foam from the dollar store (which is thinner than any of the sheets at Michaels) and am still having trouble.
I believe Anahita meant pre-cut circles, not just sheets of adhesive foam. The pre-cut circles are already adhesive on the entire bottom, which means you can't miss an area with glue, which means they should stick down better and more completely. You just place 'em down and you're done. I think a few mers have given up punching all their circles because of the immense effort involved, and probably in fear of RSI haha. But if you're managing to make it work, awesome! :)

[PearlieMae]

While I don't use plasters in my tailmaking, The Compleat Sculptor ( http://www.sculpt.com ) has a variety of plasters to choose from:

http://www.sculpt.com/catalog_98/CastingMaterials/GYPSUMS/gypsum2.htm (most commonly used)

http://www.sculpt.com/catalog_98/CastingMaterials/GYPSUMS/gypsum5.htm

http://www.sculpt.com/catalog_98/CastingMaterials/GYPSUMS/gypsum6.htm

http://www.sculpt.com/catalog_98/CastingMaterials/GYPSUMS/gypsum7.htm (my favorite)

http://www.sculpt.com/catalog_98/CastingMaterials/GYPSUMS/gypsum8.htm

I prefer oil based clay (Plastilina) as it's reusable and it doesn't need a release agent.

You might be able to use polyester quilt batting to reinforce your mold as well. I used it in my resin fluke mold and it's indestructible!

[Mahi Mermaid]

You used Gypsum Cement? Is that actual cement as it sounds?

I went to Home Depot today to check out the difference in fiberglass and plaster and ended up getting the plaster (the lady put it at the bottom of my cart for me) it wasn't until I got home and opened up the bag that I realized it was the wrong stuff. It was super grainy and gray (not white and thin like the POP)

I mixed up a little bit of it anyways and massaged it over the foam scales...and then totally panicked at all the grains (looked like sand) and ran outside with my scale sheet and started spraying water on it to get off all the plaster!

So huge setback. I had previously painted on a sealer from Smooth-on so do you think I'll have to reseal it once it dries (from the water)?

I think I'm going to get the UltraCal tomorrow! Just too cold out for fiberglass and no where inside where I could work on it safely!