Molding and Casting Materials?

Tangyson · 07-10-2012, 05:01 PM

I am ready to mold and cast one of my sculpts. Now will any mold making silicone and casting resin do? Is there a recommended brand? a prefered curing time, I had my eye on some silicone and resin that is sold on ebay. I dont want to make the investment and then get the wrong materials, so any input would be greatly appreciated.

spawnyvsbatman · 07-11-2012, 08:19 AM

Quote:

Originally Posted by Tangyson

I am ready to mold and cast one of my sculpts. Now will any mold making silicone and casting resin do? Is there a recommended brand? a prefered curing time, I had my eye on some silicone and resin that is sold on ebay. I dont want to make the investment and then get the wrong materials, so any input would be greatly appreciated.

Hey Tangyson,

I would highly recommend http://www.smooth-on.com/ Smooth-on products for silicone I would use their Mold Max 30 and for resin I would use their Smooth-Cast 305 which has a Pot Life: 7 min. enough time to mix and pour into your molds and a Demold: 30 min.

Hope this helps you out.

Thanks,
sPAWNY

Tangyson · 07-12-2012, 08:18 AM

Thank You, Spawny I have checked out the web site and I am leaning towards to buying. One more question, How do you measure to mix the two parts of liquid? For example the resin says its a 1-1 and the silicone says its a 10-1 then theres some parentheses under it that says scale required. Once again I really appreciate your info.

Alaneye · 07-12-2012, 08:30 AM

Quote:

Originally Posted by Tangyson

Thank You, Spawny I have checked out the web site and I am leaning towards to buying. One more question, How do you measure to mix the two parts of liquid? For example the resin says its a 1-1 and the silicone says its a 10-1 then theres some parentheses under it that says scale required. Once again I really appreciate your info.

It's usually best to measure these things by weight. So for the 1:1 resin, if you measure 200gms of part A, you measure 200gms of part B so you end up with 400gms of resin. It's best to measure them in two separate containers, then mix them together after you have the correct weight.

With the 10:1 mix, for every 10 parts of the silicone, you mix in 1 part of the hardener. So for 100gms of silicone you would add 10gms of hardener, for 50gms of silicone you would add 5gms of hardener.

It's usually best to measure in easy to calculate amounts.

Al

beaker · 07-17-2012, 04:00 PM

If I may, you could try our Mold Star 15 (or Mold Star 30) as opposed to the Mold Max 30, it is easier to use being 1:1 by volume, in other words, dixie cup of 'A' & dixie cup of 'B' and de-airs itself nicely... has good overall physicals and more archival than Mold Max. For Texas, you can buy right from Reynolds in Texas:
Reynolds Advanced Materials
13700 North Diplomat Dr.
Farmers Branch, TX 75234
(800) 421-4378
www.reynoldsam.com
Hope that helps!
Oh, btw... 'hi', I am new on the site but LOVE the hobby.. hope to make a contribution when and where I can!

beaker · 07-17-2012, 04:12 PM

One other note on buying silicones, resins, or urethane rubbers on ebay... all these materials, whether it is ours or not, have a shelf life. Generally speaking, it is 6 months for silicones and 1 year for urethanes from date-of-manufacture unopened... again, all manufactures have a similar policy, so before considering an ebay purchase of this stuff... caveat emptor

beaker · 07-17-2012, 04:18 PM

one more thing (sorry) IF you can handle the faster potlife of Smooth Cast 300, I would recommend it over the 305... as long as you have your ducks in a row, 2.5 minutes should be plenty of time to mix and pour... the reason being, urethanes have isocyanates in them, in the raw state, these are chemically destructive to a mold material to varying degrees. The longer a resin sits uncured on the mold surface, the longer the chemical composition has to react with the mold surface... a fast setting resin does not sit that long on a mold surface so if everything else is equal, you will get more castings from a mold rubber with a faster setting resin than one that is slower...

Tangyson · 07-17-2012, 05:50 PM

Thank You, Thank You, this is all really useful info. Im going to consider trying your recommended mats Beaker a 1 1 mix seems more easy for a first time cast. So if the resin curing time is lets say.. 5 mins then a couple of minutes after the pour the cast should be ready to take out?? Same with the silicone?? I dont remmember were i read that like a whole day was prefered for curing time on both materials is this in anyway accurate?? Also is a pressure pot recommended? I was planning to use one but if its not necessary then well.. one less step you know. And Welcome to the forum its great to have helpful members.

beaker · 07-17-2012, 07:14 PM

Thank you for the welcome... you can potentially demold the casting after about 20 minutes (if using the Smooth Cast 300) and use the rubber mold in as little as 4 hours (even sooner if you subject it to mild heat) Tin cured silicones such as Mold Max are less sensitive to the addition of heat and do take a full day to cure... this is really true about most tin-cured silicones....
Here is the thing about pressure pots... anything benefits from being cast under pressure, just remember, if you want to cast under pressure, you need to make your mold under the same amount of pressure you will be casting in.... another note...it is all about mold configuration, sometimes an improperly vented mold will still achieve a good casting if done under pressure... with a properly vented and well made mold, a little baby powder dusted in the mold will allow the resin to flow over the surface and not have air entrapment issues without the need for pressure casting... but as said, all benefits from pressure casting but sometimes it is hard with a really fast setting resin... those are the pros and cons...

beaker · 07-17-2012, 07:30 PM

Quote:

Originally Posted by Alaneye

It's usually best to measure these things by weight. So for the 1:1 resin, if you measure 200gms of part A, you measure 200gms of part B so you end up with 400gms of resin. It's best to measure them in two separate containers, then mix them together after you have the correct weight.

With the 10:1 mix, for every 10 parts of the silicone, you mix in 1 part of the hardener. So for 100gms of silicone you would add 10gms of hardener, for 50gms of silicone you would add 5gms of hardener.

It's usually best to measure in easy to calculate amounts.

Al

totally agree that measuring by weight is usually better, especially if only doing a few grams at a time, the smaller the pour, the tighter you need to be in ratios... that being said, always read the technical bulletins that come with a product because sometimes a 1:1 by volume ratio does not always equate to a 1:1 by weight mix... in the example here of the Smooth Cast 300 or Smooth Cast 305, it is a 1:1 by volume but a 100:90 by weight... if you did it 1:1 by weight you would have an improper mix ratio and could be in for trouble... and as said.. you gave great recommendations! One thing I would add, especially for thicker materials is to do a mix-pour-mix routine, in other words, mix A & B in one container then transfer it into another container and mix again. This will ensure no uncatalyzed material that could be clinging to the container wall or bottom....