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Old 11-11-2011, 02:33 PM   #103
redprimo
Gnarly Adventurer
 
Joined: Jul 2011
Location: central coast of California
Oddometer: 340
Quote:
Originally Posted by HickOnACrick View Post
Do you have this backwards? I am under the impression that the greater the surface area exposed to air, the shorter the pot life??
Not for polyester resin. Polyester resin is an exothermic reaction and heat is also an accelerant to the reaction. if you contain the heat it will go off faster. That is why resin in any bucket always goes off before the lay up. Likewise if you use a large diameter bucket and increase the surface area and minimize the thermal mass you will extend the pot life. My tip about pre weting the cloth is also a way to extend the pot life. The pre wetted cloth if left flat will not go off as fast as the resin in the bucket.

I used to have my own pattern and mold business and before I had any employees large layups would get a bit crazy. I would mix resin and paint some on the mold then wet out a piece of cloth and fold it up and transfer it to the mold and un-fold it but not roll it out, then pre wet another layer and leave it on the table while I rolled out the first piece of cloth.

I have never used a paint roller to apply resin, it is too slow. I aways pre-weted the cloth by pouring the resin on and then using a bondo spreader to move it around. When I mention rolling out the cloth I am refering to using a ribed metal roller to get rid of any air bubbles.

All that I have written also applies to epoxy but the effect of using a shallow bucket on 40 minute epoxy is less than on polyester resin.

You may be refering to high humidity reacting with epoxy resin and making it kick faster. I live in California and have no experiance with this so some one who does will have to chime in.
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