silmar woes

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JRay8

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Joined
Jul 4, 2011
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280
Location
Arnold, MD
ok, i keep having trouble casting silmar. i can mix it the same every batch and get different results each time. mostly it does not set. i have had to put it in the oven to get it to harden. my wife didnt like that much. and when i have gotten it to set it was really brittle. almost powder like and had lots of voids. is there a secret dance or prayer that goes along with this stuff?​
 
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Crickett

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Mar 22, 2009
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Saskatoon, SK CANADA
I don't cast with silmar but you should invest in a toaster over and stop using the oven in the kitchen, I don't think fumes and food would taste very good, let alone the effects on your health.
 

JohnU

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Jan 31, 2008
Messages
4,951
Location
Ottawa, Illinois
I've been using Silmar 41 for years with no problems. At least no problems curing. It cures with heat but too much heat and it gets brittle. I use 3 drops of catalyst per ounce of resin. I stir until it turns a greenish blue tint, then add the color dyes if coloring. I let it set for 24 hours before even attempting to use it. I usually use a pressure tank and set it in a warm place. If your shop is cold, hang a clip on light above the cup of resin prior to adding the catalyst, to warm it up and thin it out a bit. It will mix much better and air will escape faster. The colder the room the slower the cure. Almost all of my casts come out tacky. That's just a property of poly resin. I let it set in the sun for an hour or just let warm air get to it for a little while, and the problem is fixed. I would not recommend using the kitchen oven but that's just me. If they get brittle they'll shatter real easy. Some color agents will soften the resin like oil based paints. When that happens I add a couple extra drops of catalyst to the cup of resin. ( not the ounce ). Hope this helps. Good luck, John
 
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qballizhere

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Joined
Jan 31, 2011
Messages
330
Location
Northglenn Co
+1 on a toaster oven. I will also preheat the molds, and after the pour I will put them back in the oven for 90 min. I will also heat the resin.
 

DurocShark

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Joined
Jul 26, 2008
Messages
3,622
Location
Anaheim, CA
If you're using enough catalyst but it's only setting in chunks, you're not mixing it well.

Remember, PR has lots of working time. Spend 5 minutes mixing, making sure you scrape the sides and bottom of your cup/bowl/whatever while mixing.
 

ed4copies

Local Chapter Manager
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Mar 25, 2005
Messages
24,527
Location
Racine, WI, USA.
You do realize that the amount and type of coloring agent you use can greatly inhibit the chemical reaction, thus slowing the "setting" of the blanks, don't you?

We had a burgundy that took two days to start setting. We had a black that set so fast it was a challenge to pour it.
 

ed4copies

Local Chapter Manager
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Mar 25, 2005
Messages
24,527
Location
Racine, WI, USA.
Do you charge more for those that take longer to cure:biggrin::biggrin:?Time is money, you know!
Do a good turn daily!
Don

We had a burgundy that took two days to start setting.

Didn't think of that Don!!!

We discontinued it after the second time I spilled the goo while fetching my morning coffee!!! It was clear I was not "trainable" for this one.:biggrin::biggrin:
 

JRay8

Member
Joined
Jul 4, 2011
Messages
280
Location
Arnold, MD
there are a few good things here i hadnt thought about. back to the workshop to cast some more!
 
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