Hi there!
I’m ready to do the second side of gloss coat on my board and I’m out of catalyst apart from some old stuff I’ve found.
Do you think it’s OK to use? . . . I reckon it’s about five years old. . . Does MEKP go off with age?
Monty
MEKP does lose some potency with age. I’ve used some that was twenty years old, with success. As a precaution, I mixed it about 10% hotter. Seemed to work fine. Do a small test batch first, to get a sense of the set time.
MEKP doen’t polymerize with itself, However peroxides in general can decmpose over time but as long as there are no crystals in the bottle it should be active and safe enough to use. two other options can be 1) sacrifice 1 oz of resin or so to test the MEKP( and while your at it maybe do that ding repair you’ve been putting off) 2) a quick run to your friendly neighborhood walmarts automotive department and pick up some bondo hardener.
Happy monday Chris
MEKP = Methyl Ethyl Ketone Peroxide.
Which, like all peroxides, breaks down pretty easily in heat or sunlight. That’s why H2O2 ( hydrogen peroxide) is sold in dark brown bottles.
Generally,and for the sale of safety, it’s cut with a lot of relatively inert stuff so it won’t break down right away. Pure MEKP is a high explosive, by the way - and I’d imagine the reaction ain’t all that hard to trigger.
Now, if the stuff has been in sunlight, heat ( above, lets say, 70°F ) or it’s five years old and you’re not sure…I’d bag it. More is pretty cheap, and you’d Really Hate having to scrape off the gloss coat that ya just put on if it only hardened to a gummy consistency. Thin layers like gloss coats really need to be well catalysed.
By the way, MEKP keeps pretty good in a refrigerator. Dark and cold, y’know? Just label it Really Well.
And…I’ll just bet you can guess why I’d suggest bagging the old stuff. Yep, I got caught once, and used some very old catalyst, with just those results. The gummy, partly catalysed resin doesn’t sand off real well. It does clog sanding discs like sanding freshly chewed gum.
hope that’s of use
doc…