Hi guys so i recently glassed the fin box with 60ml of resin and catalyst at 1,7% 2minute mixing …starting the job and after only 4 minute It already started to gel(6 minute Total)…damn i thought i had more time…so i hurried up and one of the two fin box was resulting with a few bubbles and 5 degrees of cant instead of 6,5…was pretty angry but ok not a big problem… I thought i must pay attention with next bottom lamination since catalyst /resin seems to be quite strong.so i tested a few batch of 60 ml with catalyst at 1,4%… gel time was still low…about 8 minute…not enough time for me for laminating bottom…another batch of 60ml with 0.8%cat. gel time 11minute…so im impressed…why so fast with only 0.8%cat…in the past i laminated with 1.5% cat and gel time was about 15 minute…thats why i was Little bit confused…i finally laminated with 532ml resin and 0.6%cat …gel time 12minute…i did the job but for deck im thinking about to lower the cat to 0.5%…is It too low? Ever happen to you? Am i warrying for nothing?Thanks! All glassing job was conducted at working temperature of 23 Celsius ,~60% humidity.
-Which resin?
-How old is the resin?
-How are you measuring the MEKP? Drops, weight, or mL’s?
For me, it always seems that if my resin is ‘doped’ with anything like pigment, microspheres, silica…it always goes off a little faster.
I can take 1—1 1/2 quart of 249 and shoot 10 cc of MEK into it. That usually gives me 15–20 minutes to get everything wet out and tucked. That of course is in a room heated to about 70 degrees. If the temp is falling it gives me even more time. Temperature is most likely your problem. Wild guess; but you probably live somewhere warm. Set time is all relative to temp. And two minutes to stir Poly is way to long. You’re wasting precious time. Stir it until it changes color and starts to smell. Not even 30 seconds. Work faster, quit wasting time or use less MEK. PS There are at least two types of MEK that I know of. Normal and HOT. I suppose it’s possible you were sold something other than normal.
With Poly at least; “doped” resin is always a very slow set . Knowing this from experience I always over catalyze it.
I am mostly epoxy these days. Good to know about how those affect poly resin, thanks. -J
yea maybe 30 sec is ok to stir…about temperature i thought poly wasn’t very sensitive to climate(less than epoxy for sure).anyway 23 celsius should be fine…the only solution seems to lower the catalyst …but i dont know if 0,5 %could be ok…any other reason to this anomaly gel time?
I don’t have any idea how warm or cold 23 Celsius is. As I said In the previous reply; you may have been sold a hotter MEK. Too much room for mistakes with percentages. I just do cc’s per quart or liter. It’s not the resin. So if it isn’t one of the things I mentioned; I have no clue. And Polyester Resin is way more sensitive to room temp than Epoxy. The only thing that is really affected by temp with Epoxy is thickness of the resin and its ability to spread.
1.7% cat for 2oz. of resin at 73.4 degrees is pretty hot for setting fin boxes (I use 2% for hot coats). You don’t need to stir for two minutes, especially for such a small amount, mixing it that long with that much cat is just going to cook it off faster. I only use a few drops of cat per oz. when I’m setting fin boxes, plenty of working time and it will cure overnight. I use UV for lamming now but I used to use 1% of cat.
Poke around in the archives, there has been mention of some hotter MEKP out there like McDing mentioned. His ratios are pretty much what I use, he’s at 1% cat with a quart and 10 CCs and around .75% with 1.5 quarts.