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Old 02-04-2010, 19:09   #16
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You can stick the bucket in some cool water to slow it down. This is one reason why they suggest not to use sawdust as filler........i2f
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Old 02-04-2010, 20:03   #17
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It didn't melt down because of contamination. It was because of heat which was caused by to much epoxy in a container. You have to use a shallow tray to spread it out to avoid the out of control heating. By the way, that smoke is deadly toxic.
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Old 02-04-2010, 20:08   #18
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You can sometimes produce that type of reaction even with small batches if you keep re-using the same container. The small amounts of unused mixture keep building up and all of a sudden ----
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Old 03-04-2010, 08:57   #19
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Excerpted fropm “Epoxy Chemistry”
More Here
WEST SYSTEM | Use Guides - Epoxy Chemistry

Epoxy temperature

The warmer the temperature of curing epoxy, the faster it cures (Figure 1). The temperature of curing epoxy is determined by the ambient temperature plus the exothermic heat generated by its cure.

Ambient temperature is the temperature of the air or material in contact with the epoxy. Air temperature is most often the ambient temperature unless the epoxy is applied to a surface with a different temperature. Generally, epoxy cures faster when the air temperature is warmer.

Exothermic heat is produced by the chemical reaction that cures epoxy. The amount of heat produced depends on the thickness or exposed surface area of mixed epoxy. In a thicker mass, more heat is retained, causing a faster reaction and more heat. The mixing container's shape and the mixed quantity have a great affect on this exothermic reaction. A contained mass of curing epoxy (8 fl. oz. or more) in a plastic mixing cup can quickly generate enough heat to melt the cup and burn your skin. However, if the same quantity is spread into a thin layer, exothermic heat is dissipated, and the epoxy's cure time is determined by the ambient temperature. The thinner the layer of curing epoxy, the less it is affected by exothermic heat, and the slower it cures.

Controlling cure time ...
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Old 03-04-2010, 09:11   #20
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Making a little leeway on this thread---did you know that ordinary white vinegar cleans off uncured epoxy very efficiently. I keep a bottle in the paint locker--not the galley :
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Old 03-04-2010, 10:00   #21
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I've been doing a fair amount of epoxy lately and have been complaining to myself about how slow it kicks off but I'd rather that than the pot meltdown.
Hi Randy,

I bet you were coating with it. There are ways to speed it up, like faster hardener, warming the resin before mixing or warming the piece you're applying it to before applying. When I coat bare wood, I warm it with a heat gun before coating. Besides faster cure, you expand the air in all the wood cavities and it will contract again after the coat is on, creating a vacuum that sucks the epoxy in deeper. It also prevents the little bubbles that are the result of expanding air when it warms up from curing epoxy.

Someone wrote about putting epoxy in a bucket of water. I have seen buckets of ice used for that but you could use hot water for faster cure just as easy.

I have noticed that the more filler is added, the quicker it cures. That one wasn't described in any literature that I found. If I need a lot, I spread it out on a piece of carton for better cooling. If it's just a bit, I spread it over all the sides and bottom of a mixing cup to increase the surface area.

What unbusted experienced is caused by exothermic heat of course but as he did many similar batches and this problem only occurred with one, there was something different to that one batch. I am not surprised if contamination speeded up the curing process after I saw epoxy cure in a new but cheap throw-away cup without hardener. Contamination of epoxy is a big problem and a lot of users make many errors. Solvents have negative impact as do your finger prints. Always use clean or new mixing cups/sticks, a new throw-away brush, sand the piece you're working on and use a vacuum cleaner afterward without touching it or wiping with solvent. No tack cloths either.

When I started working with epoxy I made all those errors. As I did more projects and read more documentation, I changed my way of working and it is now close to how a surgeon operates. Prepare, work clean and fast and clean up fast when something didn't go as planned. It is actually faster and the results are much better. Every joint I make now is stronger than the material and that was often not the case when I just started.

cheers,
Nick.
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Old 03-04-2010, 17:53   #22
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LOL, been there done that: the answer is small batches (measured/mixed properly) in a mixing pot (use a new one each batch) then transferred to a metal paint tray (thoroughly cleaned between each batch; I use 2 or 3 trays per job) for application with epoxy-proof rollers/brushes (test these first).
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Old 04-04-2010, 16:34   #23
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I love West system. I've worked on an electric car project in an unheated shop so cold the stuff wouldn't kick at all. We ended up using a coffee perk to keep the epoxy and hardener warm. I've also had it go off super fast, usually because of a small container with a good depth of mix in it. Keep the epoxy and hardener cool, and mix it up, then decant to a wider pot so the thickness isn't there. That helps a lot. Cool water bath works. As does a tray full of icecubes on a hot summer day.

As for using sawdust as a filler, I've been doing that for years without a problem. I can see their point though. It would make a nasty incendiary. I've just never had it get warm at all.


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Old 04-04-2010, 16:44   #24
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Saw dust mixed with some colloidal silica is the perfect filler for visible fillets on wood (assuming the saw dust is from that same wood ;-). I think that talk about not using sawdust is only to sell their own wood colored filleting fillers...

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Old 04-04-2010, 16:55   #25
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I do lots of epoxy work and have had the hot-pot syndrome a few times. It always comes down to having too deep of a container. It's a catch 22 situation! The hotter it gets the faster it cures. The faster it cures the hotter it gets.

On hot/sunny days I keep the resin/hardener cans in a cool place. And on the hotter days I go to the slower hardeners 206 or 209.

BTW why were you using the 207? For the natural wood look?
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Old 04-04-2010, 17:14   #26
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BTW why were you using the 207? For the natural wood look?
Yup. I am doing three coats of that and four coats of schooner on everything. It's coming out pretty good so far, with the exception of this mess, of course. I'll post some pictures when I am done. Maybe you guys can get to know my pet epoxy brick.
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Old 04-04-2010, 18:20   #27
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By the way, that smoke is deadly toxic.
I believe it is cyanide gas.

I have been buying epoxy in 55 gallon drums. It wants to crystallize in the winter so I have taken to putting a electric blanket under the drum to try to maintain a constant 65-75 temp in the drum. Not a problem in the coastal SD zone for summer heat as long as I keep my pots out of the sun and the surface area large...work fast.
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Old 05-04-2010, 04:29   #28
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... By the way, that smoke is deadly toxic.
Dan
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I believe it is cyanide gas...
I believe the vapours may be toxic, but not likely deadly, and certainly not cyanide.

HANDLING PRECAUTIONS:
Avoid prolonged or repeated skin contact. Wash thoroughly after handling. Launder contaminated clothing before reuse.
Avoid inhalation of vapors from heated product.
Precautionary steps should be taken when curing product in large quantities.
When mixed with epoxy curing agents this product causes an exothermic, which in large masses, can produce enough heat to damage or ignite surrounding materials and emit fumes and vapors that vary widely in composition and toxicity.


http://www.fibertek.ca/MSDS%20Sheets...em/MSDS105.pdf
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