Does anyone know a cheap alternative to Smooth-On's plasti-paste? The stuff used for the hard outer shell of a mold? Thanks!
Outer shell for mold?
- Thread starter Hecubus114
- Start date
LeMarchand
Sr Member
Love the stuff, but indeed expensive. I guess you can use plaster (there are harder types available).
Great_Bizarro
Sr Member
Hydrocal or stone with gauze embedded in it. Never tried fiberglass resin and cloth but it might work if it doesn't react with the silicone and if it does coat the silicone with something that won't react.
MjolnirArmor
Well-Known Member
If you wanna go super ghetto... dip a towel into resin and drape it over.
That's pretty close to what I do, but you'll want to brush a couple layers of just resin on first so that it'll go into and stick to every contour.
Old t-shirts (cut up) instead of towels work great too!
Good luck!
-Sarge
Yodajammies
Sr Member
well.....
Plasti-paste is 55$ / Gallon
Resin (at least in my neck of the woods) is running 30-35$ /gal
and then Fiberglass cloth is about 6-8$
so you're not looking at TOO much of a difference in price.
I think the convenience of not having to deal with the smell, mess, and time is worth a couple bucks more.
My .02$
Plasti-paste is 55$ / Gallon
Resin (at least in my neck of the woods) is running 30-35$ /gal
and then Fiberglass cloth is about 6-8$
so you're not looking at TOO much of a difference in price.
I think the convenience of not having to deal with the smell, mess, and time is worth a couple bucks more.
My .02$
how hard is plaster to use? If I make a mold out of polyurethane rubber, would plaster be a bad/good idea for the outside?
clonesix
Master Member
gypsum is very strong, but needs to be reinforced with cheese-cloth, burlap, or something.
I say 'gypsum' rather than "plaster" so it won't be confused with Plaster of Paris, which is the weakest of the plaster families.
how difficult is that as far as demolding, weight, etc?
I'm not even sure I would know how to do it... just make a box around the mold and pour it in around it in halves?
I'm not even sure I would know how to do it... just make a box around the mold and pour it in around it in halves?
ok I just read gypsum is drywall? So just use drywall with the support cloth of some kind?
i've been using plaster of paris with drywall tape embedded in it. drywall tape is fiberglass, relatively cheap, and i do a lot of work on the house, so i have a ton of it.
plaster of paris is pretty cheap and hardens fast. while it's safe to handle in a few hours, it took about a week for mine to totally dry... until then it was still damp to the touch, but strong and functional.
first i cut up a bunch of 6" strips of the fiberglass tape. i mix up the first coat of plaster really soupy and just pour it on (with a wall built up to keep it on just one side!). slap the tape in and wait for the plaster to kick.
add another coat or two until it looks safe. mine's about 3/4" thick.
once it felt really dry... a week or so later... i sprayed it inside and out with primer. just one coat inside, but 4-5 on the outside. that was just so that it wouldn't get plaster dust all over everything.
a $30 bag of plaster of paris is good for a couple of fairly large molds and some smaller stuff.
though i'm digging the resin and towel idea... i've got a ton of smoothcast 300 that i don't really use for anything.
plaster of paris is pretty cheap and hardens fast. while it's safe to handle in a few hours, it took about a week for mine to totally dry... until then it was still damp to the touch, but strong and functional.
first i cut up a bunch of 6" strips of the fiberglass tape. i mix up the first coat of plaster really soupy and just pour it on (with a wall built up to keep it on just one side!). slap the tape in and wait for the plaster to kick.
add another coat or two until it looks safe. mine's about 3/4" thick.
once it felt really dry... a week or so later... i sprayed it inside and out with primer. just one coat inside, but 4-5 on the outside. that was just so that it wouldn't get plaster dust all over everything.
a $30 bag of plaster of paris is good for a couple of fairly large molds and some smaller stuff.
though i'm digging the resin and towel idea... i've got a ton of smoothcast 300 that i don't really use for anything.
Tim Allen
Sr Member
well.....
Plasti-paste is 55$ / Gallon
Resin (at least in my neck of the woods) is running 30-35$ /gal
and then Fiberglass cloth is about 6-8$
so you're not looking at TOO much of a difference in price.
I think the convenience of not having to deal with the smell, mess, and time is worth a couple bucks more.
My .02$
If dont need a gallon of homedepot resin to make a outter shell, you can get a quart or whatever the next small size is for like 10 12 bucker and the fiberglass matte for another $8
Dont waste your time on the smoothon stuff ive pulled out over 20 helmets from this mold and the shells doing just fine
Great thread!!
Question--does the silicone jacket/mold need a release agent applied before doing the 'glass outer jacket? Or will the fiberglass not stick to silicone?
Question--does the silicone jacket/mold need a release agent applied before doing the 'glass outer jacket? Or will the fiberglass not stick to silicone?
If dont need a gallon of homedepot resin to make a outter shell, you can get a quart or whatever the next small size is for like 10 12 bucker and the fiberglass matte for another $8
Dont waste your time on the smoothon stuff ive pulled out over 20 helmets from this mold and the shells doing just fine
I have limited experience but I can say with some certainty that not using a release agent would cause a lot of frustration...
clonesix
Master Member
Nothing sticks to silicone RTV, except itself. You don't need a release.
Gypsum is plaster. I don't like to use the term "plaster" because it brings to mind plaster of paris, whic is the softest, weakest of plasters. An example of gypsum would be: hydrocal, hydrostone, ultracal (gysum +portland cement).
Drywall is gypsum, not the other way around.
Gypsum is plaster. I don't like to use the term "plaster" because it brings to mind plaster of paris, whic is the softest, weakest of plasters. An example of gypsum would be: hydrocal, hydrostone, ultracal (gysum +portland cement).
Drywall is gypsum, not the other way around.
really? The last time I took a pull from a RTV mold - I didnt use a release and it really clung - like pulling a bandaid off... maybe just from the intricate parts...
