Casting material?

[ynneb]

I am wondering what is a material that can be cast like plaster, has the cheapness of plaster, Is rapid setting, but has good strength like resin, but in not resin?

Any ideas?

[Konstantin]

Concrete maybe?

Some other construction materials, those arent expensive. To lighten up concrete you can mix it with something very light like those small balls of plastic used in packaging, dont recall the name. poliestirene?

[High Seas]

ynneb - Benny
have you checked Nuplex (dont recall their operating name in OZ) they've always been a big help in NZ - also ATI - Adhesive Technologies. Nuplex mixed some stuff (vinylester) up for me and even "promoted" (resin term) just to my specs for cure time/temp.
Hole that helps - cheers - Jim

[ynneb]

Thanks Guys, I like the sound of vinylster. I did a search on it, and it does sound cheap and strong.

I want to route some fancy picture frames and make moulds from them. I want to ba able to cast the frames and then paint them fancy colours. High seas, do you know if paint will stick well to vinylester?

[High Seas]

Benny -
its very similar to polyester resin - it just wont adsorb/absorb water - thats why its used in swimming pools and water tank repairs! Its often use in boat bottoms for that reason too. Nuplex has got some neat handouts they gave me - but mine are onboard in NZ so I can't send em to ya.

It can painted with anything that sticks to polyester resin. You can add dyes to it as well to color it as its laid up. Will you be casting with or without reenforcement ('glass)? How thick - I ask as it is exothermic and can get hot as it cures - if you tell them (Nuplex/'ATI) they might have a 'promoted version that will layup thicker. Else you can lay up a bit at a time prolly 1/4 inch or so?
Is this for the sea-shell frames - they look real cool.
cheers - Jim

[jc56au]

Adding fiber to plaster will strengthen it considerably. Same principle as fiberglass. Old type plasterers used hair but probably paper fibers are easier to get/make and would give finer detail. Egg cartons are a good source. A old book quotes about 2% will double the impact strength and more is better.

The limit is really how much you can add to the water and still be able to mix with the plaster and mould with it, it gets difficult above a couple of %.

[thuffner3]

There are any number of cementious products available from local flooring compainies.
US Gypsum sells one product for casting, you have to look under USGYSUM for casting products.

I've done some pretty neat things with a product called Plani-Patch made by Mapei. It's a flooring installers filler material.

J2C
Neil

[gcz]

i've had great casting success by mixing bondo with liquid polyester resin (for 2 reasons - bondo is cheaper and also the filler reduces the heat of curing so you can do thicker stuff)
make it liquidy enuff to pour properly and debubble
use minimal catalyst to not have a fast hot cure - it can actually burn on a very thick piece!
i used to make tons of round corner baseboard pieces for the bullnose sheetrock corners this way
i cast them in very expensive silicone rtv, but using a wood model, it gave wood grain to the pieces and painted, they looked really good.

[mxtras]

I know it may not be huge concern to you, but I have found that polyesters suck for molds because of exotherms and shrinkage but I guess (just like everything) it depends on what you are doing.

One product I used that I was pretty impressed with was Chock Fast Orange - it is an industrial potting compound used to set engines and such for large applications. It has negligible shrinkage - even in large volumes. I can't recall the cost - I think it was about $40 for a 1.5 gallon kit - far more expensive that plaster, I suppose....probably not what you want, I donno.

Just watch out for the exotherms (curing heat) if you decide on polyester or other catalyzed resins, ynneb. Don't mix 'em too hot - keep the thicknesses to a minimum be careful duplicating plastic parts that you wish to preserve - they may be destroyed by the heat.

Scott

[mxtras]

Boy - I missed the whole point of the whole darn thread - sorry.

...I am a bit drugged up (precriptions) at the moment.....you are looking for the material to cast into a mold, not the material to make the mold from....sorry.

I agree with whoever said to add fiber to the plaster. I go with that idea for cost and simplicity reasons.

I have nothing else to say. I am going to take a nap...oh, wait - I am at work. Damn.

Scott