I see that Silmar 41 is popular for casting. I saw a You Tube where a guy uses a Resin from Michaels. Does anyone have experience with it?
Castin' Craft® Clear Polyester Casting Resin
Castin' Craft® Clear Polyester Casting Resin
Michaels PR for casting
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Very similar in chemistry. Use it all the time, usually with 40 percent off coupon.
jttheclockman
Member
I started casting with it but switched early on because of the price. It seemed to cast harder too as to Silmar which cast a bit softer in my opinion and is less heat. Just an opinion. It still is a good casting resin if you know the shelf life of it. Sometimes in those small stores it can sit on the shelf a long time. I always knew silmar is fresh when shipped.
Castin craft is perfectly fine for casting. Many of us use it. The Shore hardness is harder than Silmar but they are both Polyester resin. That extra hardness can be tricky to turn and put it close to acrylic acetate it terms of brittleness. Additionally, too much mekp, which is the catalyst, can make it brittle as well. And so can just a bad batch of PR.
If you cast a 5" blank, you'll use about 2 ounces of resin or less per blank and 6-7 drops of mekp per blank will usually be enough.
Silmar is cheaper overall from USComposites, about $50 or so per gallon with shipping. But, if you're only casting a few blanks at a time, it may not be worth it if you're not going to cast a bunch in a relatively short time. A can of casting craft will get you about 15 blanks.
A good can of casting craft should slosh around a little bit. If it doesn't, I'd look for one that does.
If you cast a 5" blank, you'll use about 2 ounces of resin or less per blank and 6-7 drops of mekp per blank will usually be enough.
Silmar is cheaper overall from USComposites, about $50 or so per gallon with shipping. But, if you're only casting a few blanks at a time, it may not be worth it if you're not going to cast a bunch in a relatively short time. A can of casting craft will get you about 15 blanks.
A good can of casting craft should slosh around a little bit. If it doesn't, I'd look for one that does.
Castin' Craft is made by ETI, and Silmar is made by Interplastic Corp.
Manufacturer's use different formulations and they cure differently.
It's a misconception that too much catalyst (in this case MEKP) causes the cured product to end up brittle or chip easily. It isn't the amount of catalyst, it is the exotherm that causes this issue. Polyester resin is pre-promoted and the catalyst accelerates the exotherm initiating the crosslinking. Too much heat can cause fracturing in the crosslinking.
In lower temperatures, more catalyst may be required to initiate the exotherm, and the opposite is true with higher temperatures. Also, depending on the amount of resin being used, the amount of catalyst needs to be adjusted. With 2ozs, it would require more catalyst than when using 15ozs.
Manufacturer's use different formulations and they cure differently.
It's a misconception that too much catalyst (in this case MEKP) causes the cured product to end up brittle or chip easily. It isn't the amount of catalyst, it is the exotherm that causes this issue. Polyester resin is pre-promoted and the catalyst accelerates the exotherm initiating the crosslinking. Too much heat can cause fracturing in the crosslinking.
In lower temperatures, more catalyst may be required to initiate the exotherm, and the opposite is true with higher temperatures. Also, depending on the amount of resin being used, the amount of catalyst needs to be adjusted. With 2ozs, it would require more catalyst than when using 15ozs.
plantman
Member
Works great if fresh, but has a very short shelf life. Less after opening. If you see cans that do not have the catalysis included, avoid them, they are old stock and probably hardened in the can. Shake can to make sure this has not happened. I ran into 4 cans in our local Michael's that were solid. I told the store about them, but they were still on the shelf two weeks later. Jim S
jttheclockman
Member
So bottom line is too much catalyst causes brittleness
You say tomato I say tomaaato Too much catalyst caused too much heat. (just funnin)
Sabaharr
Member
I also got my wife to get a can from Michaels. She works there and gets a discount on top of the 40% off coupon (SWEET). She brought it home and it was a rock in a can. This was from a new store that had been open just a week. We went back and the whole stock was hard in the cans. It was instantly removed from the shelf and another can was brought to me from another store the next day after it was checked for being liquid. I told the manager, who went to pick it up 25 miles away, to shake the can but don't open it. It cast some fine blanks for me. The store ordered new stock which I went through in a short time and the stock now gets rotated regularly by me buying it. I just wish they would stock the pearl-ex colors in the larger bottles instead of the sampler kits. I have to order them elsewhere. Hobby Lobby has about 6 colors but you need more choices than that. So to answer your question it works just fine if you don't get carried away with the MEKP, which is sold separately from the can of resin. If you want to try it out I suggest you clip a coupon or look for one online. 40% is a lot to get taken off the price. Sometimes they have a 50% one too.
Eric1075
Member
I've just gotten into casting myself using the Castin Craft Polyester Resin from Michael's. If you havent already discovered, use it in a well ventilated area. This stuff stinks. From what I was told Alumalite is odorless. The other thing with the PR is the work time is tricky to figure out. To quote another member, PR goes from water to snot to solid very quickly. I found this out the hard way. I left my shop for 5 minutes and it started to thicken, then set. What was supposed to be a two color swirl ended up being 2 single color bottle stopper blanks. Lastly, its recommended to use a pressure pot when casting with Alumalite. Not the case when using PR. Good luck!
Mondo
Member
Can you pour multiple layers with casting craft? 1 color layer let cure, pour clear layer let cure, pour final color layer? Or how about 3 layers of clear?
jttheclockman
Member
Yes When you say cure I say set. Not totally dry
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Mondo
Member
Thank you sir!
I know it is an old post but saying that Alumilite is odorless is sort of a misnomer. Alumilite does off gas as it is mixed and curing, the odors are not as strong as PR but I would not want to directly breathe either one. Always use both in well ventilated areas and use a respirator rated for chemical vapors or at a minimum an N95 mask rated for chemical use.
CrimsonKeel
Member
this right here is right.
just cause a chemical doesn't smell does not mean it isnt bad for you. alumalite part b is an isocyanate. aka bad stuff for your lungs and skin.
this is straight from and msds
"Chronic Inhalation: As a result of previous repeated overexposures or a single large dose, certain individuals can
develop isocyanate sensitization (chemical asthma) which will cause them to react to a later exposure to isocyanate at
levels well below the TLV. These symptoms, which can include chest tightness, wheezing, cough, shortness of breath, or
asthma attack, could be immediate or delayed (up to several hours after exposure). Similar to many non-specific
asthmatic responses, there are reports that once sensitized and individual can experience these symptoms upon
exposure to dust, cold air, or other irritants. Sensitization can be temporary or permanent. "
http://aldax.com.au/msds_tds/msds/Alumilite Clear.pdf wear a chemical respirator and proper PPE