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Unless you really like second-rate results, or you want to be disappointed, don't bother with "homemade" release agents. The commercial ones are cheap for what they do, reliably and correctly.

Getting how-to info from the manufacturers of the various products involved generally works much better than getting second-hand info from people who may or may not have actually used the stuff.

There is a very well done video library at this site all about making masters, molds, release agents, etc. It's worth the time to watch, even if you think you know what you're doing.

 
There are also some excellent tutorials at this site, as well as additional videos.
 
 
 
 
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Here's another excellent video on making 2-part molds specifically for model car bodies. This one focuses on the PlatSil line of casting silicones from Polytek, many of which I've used (as well as those from freeman). This is also a very worthwhile video, even if you already know something of the process.

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Depending on the type of part you are doing, and how many of said part you want, you may not even want to use a mold release material at first.  Starting out, you'll be trying smaller parts anyway.  Those can usually be done without anything, though that will shorten the life of the mold.  I used to use the silicone mold release (in a spray can) only for large parts like bodies and hoods, when I did those.  You can overdo it with that stuff.  I've heard of people having trouble getting all of the mold release off of bodies from one particular caster.  If you go nuts laying that stuff on, the excess will absorb into the resin and cause problems.  Depending on the design of the mold, it's going to produce X number of parts before it starts to degrade.  The RTV material will start drying out (due to heat generated by the curing of resin within the mold) in areas like door lines and windshield wiper detail, and there's nothing that can be done to stop it.  Careful application of mold release will help you get more pours off of a mold than you would get without it, but "too much" won't extend the life of the mold any further.  

For small items like wheels and engine parts, I use talcum powder.  Get a small container with a lid that snaps on (like a margarine or Cool Whip tub), put in a few molds and some powder, snap the lid on tight, and shake the thing around to give everything a nice even dusting.  You don't want any clumps of powder in the molds.  The powder breaks the surface tension letting you fill the molds more quickly and with less messing around.  It absorbs into the resin but doesn't cause any problems.  If you are painting the parts or sending them out for plating, you don't have to go to nearly as much trouble to clean the parts as you would have to do if they had silicone or greasy stuff on them.  I've had thousands of parts plated after casting them with this method.  Any reject parts were due to foreign matter getting into the vacuum chamber during the plating process.  I've never had parts disintegrate or degrade because of the resin itself, as long as it was properly mixed and in the correct A:B proportion.  If you've got parts from a pour that wasn't mixed correctly, you'll figure that out long before you attempt to clean them or do anything else with them.

One instance where mold release is an absolute must, is when you make a multiple-piece mold and you are pouring new rubber against previously cured rubber.  This stuff sticks to itself like you wouldn't believe, so you've got to have something between the old layer and the new one or your part will be trapped in the mold.  I've used leftover liquid car wax for this, painting it onto exposed rubber with a cheap paint brush.  Some of the waxes are colored in the bottle, and change color as they dry.  That makes it easy to make sure you've covered everything that needs to be covered.  Make sure you cover all of the exposed rubber.  You don't need to apply it to still-exposed portions of the part from which you are making the mold.  

Starting out, you're probably better off going with all products from one company.  Certain resins won't cure fully against certain types of mold material; that sometimes happens when you pour one company's resin into another company's RTV.  If you use one company's materials all the way through, you'll get decent results sooner and with less frustration.  There's plenty of time to experiment later, after you've seen positive results. 

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Talcum powder, eh?

I've heard this multiple times, and all I can say is that I've been making parts for product-development presentations using the same materials used for making resin models and silicone molds for same...as well as high end 1:1 prototype and limited-production composite parts for cars and aircraft...for over 40 years.

My parts required a professional-looking finish right out of the mold, easily paintable, etc. Parts also were often molded in specific materials, colored, or of varying hardness to simulate actual production values....so painting was out of the question.

I've only used the mold-release agents recommended specifically or supplied by the manufacturer and...surprise...I've never had any problems IF I read the instructions carefully and followed them, using a modicum of common sense.

In the OLD days, we'd use multiple coats of wax. Absolutely and completely obsolete with today's mold-release agents.

I've seen guys use PAM, vaseline and olive oil too. I'll pass. B)

NOTE: I'm NOT saying Mark is wrong. It's just not the way I do things. :D

Edited by Ace-Garageguy
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http://www.alumilite.com/store/p/965-Synthetic-Clay-1lb.aspx

 

This is what I use for clay.  I think this might be re packaged KLEAN KLAY, but uncertain.  I think you might find this to be the best deal for mail ordering.  It is $4.75 a pound.  I bought about twenty pounds a few years ago for half this amount.  Real KLEAN KLAY can be very expensive.  The clay you need, needs to be Sulphur free otherwise the silicone that touches it will not cure.  I highly suggest the Alumilite price.  Even with postage the price will be a real deal.  Hobby Lobbies do carry some of their products too.  My first casting experience was with a Alumilite kit but I quickly moved on.  Now I just Drive to Tempe, AZ and buy anything I need fresh right off the shelf.  If I have problems I just ask them.  If you are wanting to attempt to make rubbery like tires I would suggest you try POLYTEK PT FLEX series, this product cures really quickly.  Unfortunately SMOOTH - ON has nothing like the FLEX SERIES, this product is very expensive too.  Just get some black dye and color the material.  You can also paint the inside of a mold too.  Let the paint fully dry, pour in resin to cure and then pull out a painted part.  You can even be a really crappy painter too, it won't matter.

Edited by Greg Wann
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  • 2 months later...

Freeman Pattern Supply carries 202 Pattern release and Paintable silicone spray release . I use them for my casting. 202 is basically a Vaseline in a spray can. Used to keep two part molds from sticking together when you pour the second half. Paintable spray release is just that. You can paint the part after you cast them.

pattern-release-202.jpg

silicone-spray.jpg

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Freeman Supplies carry's everything you need. I uses 202 pattern release for two part molds to keep the second pour of rubber from sticking to the first pour. Or you can use Vaseline. And they carry paintable silicon release for the mold. Best to use this for molding as it will not leave silicon behind that you cant wash off but lubs the mold.They also carry Sulfur less Plastisine clay which will work with silicon molds. Will not react to the silicone.

silicone-spray.jpg

pattern-release-202.jpg

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I've been casting resin for years - mostly parts like wheels, tires, engines, etc., but some bodies too.  I use Permatex red hi-temp RTV to make the molds.  It takes fine detail and even tiny projections like holes in disk brakes can last for quite a few casts.  I mix the RTV on a smooth plastic cutting board adding about 1/20 by volume baking flour, repeatedly (about a minute) spreading the mixture out, giving it a chance to absorb some atmospheric water.  Mold thickness of up to 3/8 is no problem.  Sawdust can also be mixed in after the first layer of flour plus RTV for a thick, more rigid mold.  I use petroleum jelly dissolved in mineral spirits as a mold release agent on the piece to be copied (let it dry), and on the mold if it has vulnerable projections.  I like MicroMark CR-300 resin or the SmoothOn equivalent;  Alumilite puts off vapor I can't stand.  I usually wash castings with soap and water before applying water-based paint.  Good luck and I hope you enjoy casting as much as I do.

Edited by GerN
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It always boggles my mind when folks make resin casting more complicated and messy than it has to be. Sure there are plenty of ways one can do this, even have some luck with decent parts but do yourself a favor and research a little. Do not use weird anything as mold release. Many if not most mold releases in a spray can are rebadged Price Driscoll products which can be purchased from them directly. My go to release is Price Driscoll PAR4 Parfilm paintable mold release. Its fantastic. Thats that. Ive used Alumilite and Smooth On resin and RTV and find each has their own benfits depending on what type of parts you are trying to make. For someone starting out, a small batch of HS2 mold rubber from Alumilite is extremely easy to work with. Also Smooth On 14NV is great. Alumilite white is fantastic beginner resin also. For consistentcy and quick cure times, a tip would be to pre-heat your molds prior to pouring resin. I use a griddle set at 150C. Heat the molds until warm then pour your resin. I set the molds back on the griddle often times to speed the curing process. This is extremely helpful with very tiny molds with small parts. I lightly dust my molds with talcum powder using a bushy paint brush. I give my molds a quick spray of mold release every 3-4 pulls also, this greatly helps pulling parts from your molds more easily. Having safety cut glass as a work base is also very helpful as you can mold release it and scrape off resin with a razor and keep it clean. Do yourself a favor and watch some videos such as Bill recommended. The Alumilite DVD is also very well made and informative. The issue with resin casting is that lots of folks have their own opinion on how to do it. While some of their methods may "work," a great deal of what is recommended  is overly complicated, overly messy, and will produce crappy and sloppy molds and parts with poor results. Listen to Greg and Bill as they know what they are talking about. No offense to anyone else chiming in. My parts were always clean and bubble free and my customers were always highly impressed with the quality so I may know a thing or two as well. Good luck. 

Edited by shucky
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I use a little vaseline mixed with Naphtha as a mold release. This works great and is about the cheapest thing you can get. Personally, I like to use industrial silicone for my molds rather than ones that are marketed towards model builders and hobbyists. I find the industrial silicones are incredibly strong and will hold up through many pulls.

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Here are a couple of photos of my recent castings, based on the Revell Ferrari California.  The first shows the mold and a casting straight from the mold.  The second shows a chassis (using two of these castings) I'm doing for my Talbot 150 Record custom.  This CR-300 is very similar in workability to slightly softer styrene.  The Permatex red RTV for the mold cost about $3 and the CR-300 about $1.50.

 

IMG_0486b.JPG

IMG_0487b.JPG

Edited by GerN
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It always boggles my mind when folks make resin casting more complicated and messy than it has to be. Sure there are plenty of ways one can do this, even have some luck with decent parts but do yourself a favor and research a little. Do not use weird anything as mold release. Many if not most mold releases in a spray can are rebadged Price Driscoll products which can be purchased from them directly. My go to release is Price Driscoll PAR4 Parfilm paintable mold release. Its fantastic. Thats that. Ive used Alumilite and Smooth On resin and RTV and find each has their own benfits depending on what type of parts you are trying to make. For someone starting out, a small batch of HS2 mold rubber from Alumilite is extremely easy to work with. Also Smooth On 14NV is great. Alumilite white is fantastic beginner resin also. For consistentcy and quick cure times, a tip would be to pre-heat your molds prior to pouring resin. I use a griddle set at 150C. Heat the molds until warm then pour your resin. I set the molds back on the griddle often times to speed the curing process. This is extremely helpful with very tiny molds with small parts. I lightly dust my molds with talcum powder using a bushy paint brush. I give my molds a quick spray of mold release every 3-4 pulls also, this greatly helps pulling parts from your molds more easily. Having safety cut glass as a work base is also very helpful as you can mold release it and scrape off resin with a razor and keep it clean. Do yourself a favor and watch some videos such as Bill recommended. The Alumilite DVD is also very well made and informative. The issue with resin casting is that lots of folks have their own opinion on how to do it. While some of their methods may "work," a great deal of what is recommended  is overly complicated, overly messy, and will produce crappy and sloppy molds and parts with poor results. Listen to Greg and Bill as they know what they are talking about. No offense to anyone else chiming in. My parts were always clean and bubble free and my customers were always highly impressed with the quality so I may know a thing or two as well. Good luck. 

Shucky I agree with you !00%. People always trying to find cheep ways to build molds. This is fine if you are just casting for yourself. But I see guys trying to sell their stuff. Missing parts of the mold, full of pin holes. Just plain BLAH_BLAH_BLAH_BLAH because the want to cut corners. I believe if they want to step up there quality. They need to step up on their casting methods. Use quality supply's and better mold quality. People stop trying to reinvent the wheel. YouTube is full of videos that show what professional casters do.All I have ever used is a good quality RTV, several different mold releases, and quality resin like Smooth On. Been doing this for 35 years. Never a problem with my castings.

011.jpg

020.jpg

021.jpg

Edited by Joeys Models
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Joseph those pictures look excellent. Peter, I assure you if your molds and methods are done "right" a pressure pot is not  necessary to achieve bubble free castings. Although I can see them being very useful depending on the materials and items your working with. 

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Joseph those pictures look excellent. Peter, I assure you if your molds and methods are done "right" a pressure pot is not  necessary to achieve bubble free castings. Although I can see them being very useful depending on the materials and items your working with. 

For simple molds, if the resin is fresh, and the ambient air is dry then yes, you can cast in open air. But other than that pressure pot is really required to produce quality bubble-free casting's.

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I have pressure pots like the one above.  The twist on lid type like this is best.  BUT!!...  What you want to look for if you are in the market is a Presto brand pot.  You can find some reasonable deals on Ebay if you look hard enough.  I think the 4 quart ones I use are model A403A.  They make a nice 6 quart that fits most body molds, the model number for the two I have is A617A.  The gasket in the lid of these models fits under a lip inside the lid.  This style of lid is the one you want.  Believe me I am speaking from experience on this.  If you are looking at a pressure cooker and you can see the entire gasket I suggest that you do not buy it.  The pressure can cause the gasket to blow out and you will never get it to work right.  You will need about 62 PSI to actually crush the bubbles in the resin.  You can get one from Harbor freight and use it in a vertical position.  But then you have four fiddly things to flip down and get tightened down enough to hold pressure.  These things are real knuckle busters and are not fun to use.  You will need to refrigerate your resin to give you more time.  Once you mix the two parts of resin it is not going to wait for you.  It will start curing quickly so you will need to be fast to be successful!  There are some tricks to learn.  Mostly I am self taught.  How you clay up a part is really important too.  Venting holes in molds is important as well.  I spent $800.00 for one that Smooth - on sells.  A five gallon bucket size.  But you have to be fast because of the four twiddly knobs that have to be flipped over and tightened.  You have to be fast and focused to use it!

Edited by Greg Wann
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