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Any substitute for Smooth-Cast 300? Answered

We have our own homegrown substitute for Oomoo thanks to the local boy genius Mikey77

But is there any substitute for it's companion product, the very expensive ($100/gallon), two part liquid plastic stuff called "Smooth-Cast 300"?

Does anyone know of a way to mix an inexpensive something up and pour it into a mold and have it harden up into a strong thing?  It doesn't have to be as invincible as Smooth-cast, but .. is plaster the only option?

Update:  What am I casting?  I found a really great ornamental tile at Habitat for Humanity and want to make copies of it

Update:   I'm wondering now, what if I used something from the wall/flooring department, like Mastic?  Its about $34 for two or three gallons.  It fills gaps and hardens to such a degree that it can't be chiselled easily.  I may try this.

Update:  Tried mastic, it works but takes far too long to dry, on the order of three days or longer...  Maybe if I mixed in some corn starch (ala oogoo?)

Thank you
-foo


16 Replies

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steveastroukBest Answer (author)2013-06-22

How about polyester resin ?

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foobear (author)steveastrouk2013-06-27

I haven't any experience with it, but I'll investigate it, thank you

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steveastrouk (author)foobear2013-06-28

"Loading" the resin with a filler increases the volume you have for a given volume of resin, reduces shrinkage, and improves wearability. Its an important trick to know about. Mix in the filler BEFORE you add the hardener though.

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PKM (author)2013-06-19

You could potentially use machinable wax if your mold can tolerate moderate heat. You can make your own machinable wax from candle wax and freezer bags (https://www.instructables.com/id/Machinable-Wax/), or buy it.

There are kitchen-science ways of making your own plastics (https://www.instructables.com/id/Homemade-Plastic/) which are super cheap in volume and sound like you'll get a decently hard material at the end of it but I have no idea about curing time, shrinkage, or how easy it is to fill a detailed mold with the soft plastic.

To be honest, while $100 is enough to give you sticker shock it's not actually terribly expensive for a whole gallon of an uncommon chemical which does exactly what you need. A gallon of silicone sealant to make Oogoo with wouldn't be cheap either (though definitely cheaper than a gallon of Sugru!) Perhaps see if you can buy smaller quantities if you only need a little bit, or split the purchase with someone else who wants to do their own casting.

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foobear (author)PKM2013-06-19

I hadn't seen the machinable wax one before. Very interesting!

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foobear (author)foobear2013-06-19

Yeah, it may come to that, I may have to spend $100.

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steveastrouk (author)foobear2013-06-22

Why ? I can buy it in pints (well, 500mL) in the UK ? Shop around. Try sculptor supply stores.

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foobear (author)steveastrouk2013-06-22

Yes I am aware that it comes in pints.

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steveastrouk (author)foobear2013-06-23

Sorry, I thought you wanted a moulding material, what you want is a casting resin instead. Try a loaded polyester resin - resin mixed with a filler like limestone.

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foobear (author)foobear2013-06-19

the homemade plastic looks too lumpy and cottage cheesey

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steveastrouk (author)PKM2013-06-22

The clues in the name : Machinable. It shrinks like a ba%$^$&rd when its cooling from liquid. Not a problem, if you're machining it

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Ninzerbean (author)2013-06-18

I've been watching a lot of videos on using 2 part expandable foam poured into molds - it's pretty amazing stuff. Let me know if that would work for what you are doing.

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mpilchfamily (author)2013-06-18

What are you casting?

Have you considered other mold options and using the Oomoo as your casting material?

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foobear (author)mpilchfamily2013-06-19

I found a lovely ornamental tile at Habitat for Humanity and I want to make copies of it.

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