I’ve started glassing my boards in a shed which is located in my back yard. Coming into the summer I find that the temperature inside this shed varies alot depending on whether the sun is shining.
Idealy I like my lams to go off in about 20 mins but with the air temps in the shed varying from 14 - 24 C (60 - 80 F) it can be difficult to get the correct quantity of catalyst to prevent the lam goign off too quick or too slow. Up untill recently I’ve always used 2% MEKP.
I’ve searched the internet for info on gel times at various temperatures and concentration of MEKP but have come up empty handed.
Does anybody out there have any data on this ??? Maybe it’s not that critical but I just need to satisfy my curiosity before I destroy a lamination.
Sounds like you do enough boards that it’s time to make a chart. Get the ounces-to-cc conversion factor and measure each batch lam resin and the cc’s of catalyst.
I glass in my garage in Kaimuki, and cannot approach two percent catalyst, a little less than one percent (say 0.875) is more like it, for a 20 minute pot life. I’m not a slow mover, either, like some newbie.
I have read that resin is strongest at about one percent - ask Ted Wilson at Fiberglass Hawaii.
I mix in whatever clean glass jars I can save from the kitchen, but before I pour, I mark the 1, 2 and 3 cup levels so I know how much resin I’m using (stingy, okay?). Then I use a 10 cc syringe to measure the catalyst, according to a chart I made up. The first column of the chart is the number of cups of resin (1 to four cups). The second column is the amount of catalyst in cc’s for 0.5 percent, the third column for 0.875 percent, the fourth column for 1 percent catalyst. It’s at eye level on the bench, so I can’t miss seeing it.
Note… the black rubber seal on the 10 cc syringes that FH sells disintegrate in about a week. The girls there replaced one syringe free (they don’t cost that much) but of course that one turned to mush pretty soon also. Now I use the barrel of the syringe as a graduated cylinder and have thrown out the useless plunger. Note also that catalyst will dissolve the cc markings on the barrel, so before first use I wrap it with some wide clear plastic tape. Months later I can still read the levels.
Am I being too careful? No. Had a warm day a week ago and VERY nearly got caught by a fast-setting batch. Some dry rails, mostly fixed with the next lam and a thick hotcoat, and careful sanding and finishing. Seriously thinking of getting suncure in my next buy, despite the additional cost and supposedly shorter shelf life.
Howzit Honolulu, Yep that was some weather we got last week. I had to wait until evening time to do my glossing. Instead of the syringes, just get some of the little maesuring cups that Fiberglass Hi. sells. Last year I ordered 1 cup and instead they sent me 100 cups, total cost was $3.00. Aloha, Kokua
Your resin supplier should be able to tell you what the gell time of the resin is with x amount of mekp at x deg. In Australia it is normally, gell time @ 2% @ 25 dec C. With that info and trying to use the same brand of resin all the time, so you get a feel for it. It will only be a matter of time before you know how much or little mekp you will need. platty.