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How to mix

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Old 06-07-2011, 05:42 PM
  #1
cotman
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Default How to mix

Feel stupid (most likely I am), but can figure out the mixing portions of epoxy surface coat. Can says measure out part A and 11 parts of B by weight. Lets say I use 8oz of A.... then how many oz. of B do I use. I know its not that difficult.. but can't for the life of me figure it out. (I know I should have payed closer attention in chemistry class). Thanks
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Old 06-07-2011, 08:07 PM
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Default RE: How to mix

So the ratio is 11 parts resin to 1 part hardener? Is this a ratio by volume or weight? What is the brand of the surface coat?

You could:

1) pour out 8 grams of hardener and muliply it by 11 which would equal 88 grams of resin (if the mix ratio is by weight)

or:

2) Measure out the resin and divide by 11 to find out the amount of hardener

or:

3) The ratio could be expressed as 100:9.1. This would yield a multiplier of .091. You could measure out the resin and multiply it's weight by .091 and add this amount of hardener. If you measured out 50 grams of resin you would then need 4.55 grams of hardener.

The mix ratio by volume is typically different than the mix ratio by weight due to the differing specific gravity. I like to mix by weight because it's much easier to mix accurately. If you want to mix by weight you need to find out what the mix ratio is when measuring by weight.

It's important to mix your epoxy surface coat very accurately. If you have too much of one part you will end up with extra molecules on the mold surface that are not linked. These molecules will then be eager to chemically link with the fresh resin used to make the parts. This issue can significantly extend the seasoning period of the mold.


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Old 06-07-2011, 11:01 PM
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Default RE: How to mix

do what I do get an egg cup full of resin then just add approx 1/4 teaspoon of MEK and it works every time M E K is the activator for resin even though they call it by another name its still MEK (methal ethal ketone)or rubber solvent just wait for mix to start changing colour and then apply ,done it for yrs and yrs everyone a winner
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Old 06-08-2011, 04:39 AM
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Von Ohain
 
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Default RE: How to mix

1: Its methyl ethyl ketone peroxide, not methyl ethyl ketone.

2: If you are using polyester, the hardening process is catalytic. Wich means, mixing ratios is not deadly important. It only affects hardening time, and hardening temperature, unless you take it to extremes and mix it way off.

3: If you are using epoxy (wich is NOT polyester), the hardening process is stoichiometric, and the mixing ratio becomes all more important for the finished product.
Methyl ethyl ketone peroxide is not the active ingredient in epoxy hardener, and if you try to use MEKP in epoxy, you are stuffed.

4: Polyester hardener is not pure MEKP. So dont go to a chemical retailer, buy MEKP dead cheap in bulk quantities and intend to use it as polyester hardener. It will fail. Polyester hardener contains more chemicals wihch is needed, although MEKP is the active ingredient.

5: I believe the thread starter said epoxy, and not polyester. Wich means the hardener is NOT MEKP. Dont use MEKP.

6: MEKP is highly explosive in its pure form (hardener is NOT pure). Do (not?) try to isolate it from the hardener and have some fun =)
Chemical properties of MEKP is quite similar to those of the terrorists favourite, acetone peroxide. Except that MEKP is liquid at room temperature.
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Old 06-08-2011, 04:52 AM
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Default RE: How to mix

MEK in an Epoxy surface coat will just make a huge mess! MEK is for polyester resin, totally different from an epoxy resin hardener.

Are you using PTM&W 1105 epoxy surface coat? I ask because that is the mix ratio for it. It is listed as resin to hardener @ 100:11 BY WEIGHT. Like Wyowindworks said, make sure it is by weight or volume before you mix, or you will not like the results. [] I would look real good on the cans, as well as the product information sheets for the mix ratio. If all else fails, give the company a call and they will be glad to answer the question for you.

Best wishes,
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Old 06-08-2011, 06:31 AM
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wyowindworks
 
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Default RE: How to mix


Quote:
ORIGINAL: Scorpion Racing

MEK in an Epoxy surface coat will just make a huge mess! MEK is for polyester resin, totally different from an epoxy resin hardener.

Are you using PTM&W 1105 epoxy surface coat? I ask because that is the mix ratio for it. It is listed as resin to hardener @ 100:11 BY WEIGHT. Like Wyowindworks said, make sure it is by weight or volume before you mix, or you will not like the results. [] I would look real good on the cans, as well as the product information sheets for the mix ratio. If all else fails, give the company a call and they will be glad to answer the question for you.

Best wishes,
Just for clarification: 11:1 is not the same as 100:11. What is the mix ratio on the can?

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Old 06-08-2011, 07:50 AM
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Default RE: How to mix

Correct, sorry if I confused someone! All my resins list it as a ratio (like 100:11) I guess the resin I listed would be a 10:1.1
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Old 06-08-2011, 06:10 PM
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Default RE: How to mix

Are you using the Fiberglast 1099 resin? I use a very accurate jewlwes scale and scoop the goop into a tared paper cup. I also include the mixing stick I use to sccop and mix the resin into the tare weight. This stuff is so thick it is nearly imposible to dispense a desired amount, so I scoop out an aproximate ammount, then weigh it. Then I multiply the weight by .011, and add that amount of resin.
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