# Smooth-on or other casting recommendations???



## John O (Mar 8, 2000)

After a long time of fooling around with RTV putty on smaller projects, I've made some masters for larger pieces and I'm ready to jump in to my first "serious" casting projects. In the past, Smooth-On seemed to be the recommended product, but looking throught their site is a bit overwhelming as to what to get for my application. What materials should I buy from Smooth-On, or whomever, for "my first casting"? 

Thanks in advance for any advice offered.

John O.


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## F91 (Mar 3, 2002)

John, I have had great luck with Tap Plastics, they aren't as overwhelming as other companies and have a decent selection.
http://www.tapplastics.com/


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## beeblebrox (Jul 30, 2003)

I've had pretty good luck with Smooth-On. The products with 1/1 mix ratio are almost fool proof and get one with a long enough set up time to keep you from rushing. A few small practice runs and you'll do fine.


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## John O (Mar 8, 2000)

_Which_ of the Smooth-on products did you use?


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## Orne (Feb 23, 1999)

I'm using the 300 and 305 casting resin. No problems, except that Smooth On has to be ordered from distributors (check their home page) and not directly from the company.


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## razorwyre1 (Jan 28, 2004)

the smooth on casting resins are great stuff. beware their 1:1 rtv's. they arent foolproof (as this fool can attest) and as many of their more popular types are urethane which means that if your casting resins in them you have to be very careful with your release agents.


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## Stimpson J. Cat (Nov 11, 2003)

Anyone try a brand called Por-A-Kast?


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## Orne (Feb 23, 1999)

I've used PorAKast, but the SmoothOn resin is better (and stay away from Goldenwest, believe that has deisel oil mixed in, found out that the hard way). For molding, I get Por A Mold S-555 for general purpose molds and the softer S-333 for detailed molds.


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## razorwyre1 (Jan 28, 2004)

pour-a-kast mark 2 is a good resin, but yes smooth on is marginally better in the character of its finished plastic. (synair seems to be a freindlier company so i generaly go with the pour a cast) i should point out that the pour-a-mold rtv products are also a urethane and therefore also a litle tricky. (when in doubt add a little extra prepolymer.) i only use them when the casting wont be resin.

for those on the west coast, you might wish to try bjb enterprises' resin(s). always good stuff.


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## fernieo (Mar 22, 2000)

Lots of info here:
http://www.polytek.com/


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## Stimpson J. Cat (Nov 11, 2003)

I've seen some beautiful casting done with Por-A-Kast but it sounds like it's no quite the best. How does it stack up to MicroMarks CR-300 & CR-600? Does anyone know who makes MicroMarks resin?


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## beeblebrox (Jul 30, 2003)

I think I read somewhere that MicroMark buys from Smooth-on and repackages it. Could be wrong.


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## razorwyre1 (Jan 28, 2004)

i think your right about that beeb.

with most casting resin of the type used for garage kits, the differences are marginal. there are some however that have great differences in character (alumilite for one). 

you can tell a lot about the companies that sell them however thier catalogs and the range of resins they carry. synair (makers of pour a cast) and alumalite seem geared toward the artist and hobbyist, and have a relativly limited range of products. smooth-on ,bjb enterprises, and silpak are geared more towards industrial users. (smooth-on seems to be the brand of choice over at lear's prototyping department, and bjb is widely used in the movie industry... although that may in part be due to proximity in both cases.) 

when im buying plain old resin, i go with synair because theyre friendly folk and there close so the shipping of a 10 gal. kit doesnt clobber me. if i need anything special, i use bjb, because they are likewise friendly, and their technical support is supurb.


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## Orne (Feb 23, 1999)

Got in the mail today a letter from Synair; they've been bought up by an English company, Hyperlast, and their new webpage is www.hyperlastna.com


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## Chuck_P.R. (Jun 8, 2003)

Orne said:


> I'm using the 300 and 305 casting resin. No problems, except that Smooth On has to be ordered from distributors (check their home page) and not directly from the company.


I've ordered directly from their website in the past, though it has been about two years, maybe they've changed that, but check into it.

I would recommend their RTV and resin. Though I would go with the higher tensil strength resin that takes about 30 minutes to set rather then the 7 minute stuff. That way you can vaccuum out 98% of the resin(not to mention RTV rubber if you get a powered, cheap, home food vacuum set) bubbles out before you pour. Make sure to shake the mold and use a harmless popsickle stick or something like that to get bubbles out of the undercuts after pouring and before placing the second half of the mold.


Buy a home vacuum set with a couple of large mason jars so you can have something strong enough to degass the RTV before pouring. You can get them from Sears or Walmart for about $100 bucks for the vaccuum device itself, and the larger mason jars will probably cost about $15 bucks.

Also pouring the RTV from a couple of feet high will help avoid bubbles while pouring as well.

I'll see if I can find my old invoices and see which ones I used.


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