Drops of hardener?

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r1237h

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Port Moody, British Columbia
I understand that for silmar 41 one adds either 5, 6 or 7 drops (I have rad all three possibilities).

Does it matter? Will it slow or speed the process, or make the material more of less brittle, if you use more or less?

Thanks
 
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It is my understanding that the more drops/ounce you use, the faster it will gel and harden and will be more brittle.
 
The optimum seems to be what works for each of us. For clear casting I use 3 drops per ounce. Adding pigments can change things. According to instructions I have read it seems that 1% MEKP by volume seems to be the rule. Doing some research there seems to be about 600 drops per fluid ounce so 1% would be 6 drops per ounce. Ambient temps, thickness of the castings, and the amount of pigments or other additives will effect the curing time. Do some experimenting and see what works for you and the type of casting you are doing.
Do a good turn daily!
Don

r1237h said:
So what is the optimum for silmar 41? I can call the company tomorrow, but hopefully someone will know before then....
Click to expand...
 
Seems like such a simple question doesn't it?

US composites recommends 10 drops of MEKP per oz of resin in the instructions they package with the MEKP.

They also recommend 1% MEKP for catalyzing on the can label. There are about 500 drops of MEKP in an oz. 1% would be 5 drops.

US Composites notes that working in colder temps may require up to twice the amount of MEKP.

The larger the volume of resin you are casting (unless you are doing large thin sheets which isn't the best choice for Silmar 41), the less MEKP you will need to get the resin cured.

I almost always use 10 drops per ounce. I like being able to turn my blanks the same day I cast them. I never have problems with chip out when turning. But I keep my tools sharp and have more than a little bit of experience in turning. 10 drops is usually optimum for me, but sometimes I'll use more or less.

You need to figure out what works best for you for what you are doing. There's only one way to do that. If you just aren't the experimental type and you really need a firm aswer, then if it is really cold (below 65F - 70F) where you are doing your casting, try 10 drops. If it is 70F to 90F, try 5 drops and see how that works for you.

Here's a link to the US Composites mixing info (in case you can't find what your supplier sent you).

http://uscomposites.com/pdf/MEKPDirections.pdf

Ed
 
I use four drops per fluid ounce and a toaster oven. Works great. They're done and ready to turn in an hour. If I rip them on the band saw fresh from the oven, the now-cured resin is still soft and cuts like butter.
 
As a general rule, I use 3.5 to 4 drops per ounce (obviously, there's a little fudge factor). But with some colors 3. It takes some experience to know what colors gel a little faster, and so require a little less mekp. For example, with black mica powder, I use 3 drops per ounce. Take good notes.
 
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