Epoxy Question: Gel time v when can I work the piece?

[Kent A Bathurst]

Hi........first time at bat with epoxy. System 3 G-2, if that matters.

I wanted a long gel time because I hadn't used it before. Went well.

I have some splined joints glued up and clamped. They say the gel time is 90 minutes, full cure at 48 hours, @ 70F. I'm at about 65F here in the shop.

Making a 6-sided critter out of 2+" x 8" WRC, splined at the joints with WO, that will end up as a 43" OD and 40" ID circle/donut/hula-hoop/garden entrance gate. These assemblies are two pairs of the 6 sides.

My question - when can I un-clamp these pieces so that I can glue them to the next pieces?

And then, when can I cut into them with a jig saw and finish them with a router?

[Howard Acheson]

Follow the manufacturer's instructions. They know best. Because you temperature is a little low, it may take a couple of hours more. I would recommend you find a way to increase the temperature in your work area at least for your glue up. In my shop we used to force cure our epoxy joints using infrared heat lamps. Using a standard set catalyst we could cure a joint in 20-30 minutes.

[Kent Chasson]

Epoxy can have a mind of it's own. Manufacturers recommendations are usually pretty conservative for clamp time but it's so dependent on temp and mixing that the only way to really know is to glue up some test pieces while you work. The stuff in the mixing pot will generate it's own heat and cure faster so don't base clamping time on the hardness of leftover glue in the pot.

By the way, a lot of people are not aware that epoxy is a known skin and respiratory sensitizer. Best to use gloves and a respirator, particularly if you plan to use it a lot.

[Larry Edgerton]

Ken

Call West System and ask for a copy of their manual. It has covered all bases and their tech line can answer any question that you may run into that is not covered in the manual. If they don't know they will do research and call you back.

While you are at it get on their mailing list for their newsletter. There are some amazing projects in it.

If you need more open time measure out your epoxy hardner in a cup, BUT DO NOT MIX IT UP. Set it in the fridge so it cools and when ready pull it and mix. If you just put the cans in the fridge it makes the pumps hard to work. As long as you dont mix it wont start to cure.

If you have a lot of glueing to do and need more time after mixing, spread the glue out on a sheet, like a baking dish. This is so there is less concentrated mass of mixed resin. the same amount of glue in a cup will start to cure considerably faster, and will even start to boil in the right conditions. Do not use plastic cups for this reason, it can melt the cup, and be careful of metal that may be hot. I save tin cans for this purpose and toss when done.

Kent is right, Epoxy has a mind of its own it seems. Heat and humidity affect it. On a hot humid day you have to be very fast. Have all your ducks in a row.

I use an infrared heater to speed cure after assembled, and if small parts I sometimes put them in the Microwave just before assembly.

Gotta get to work.........

Larry

[Mark Rakestraw]

I've used a good bit of epoxy building strip-built boats. If you used a slow cure hardener I would wait at least overnight before removing the clamps and since your shop is below the prescribed temp a bit longer before rough handling. As stated above temperature is makes a huge difference. Throw an electric blanket over it, or put a heater underneath the table the parts are on with a quilt over the top and the cure time reduces dramatically. Use care not to create a fire hazard of course. A pair of saw horses with a piece of plyood on top makes a good temp table with room beneath for a heater. I use one of those oil filled radiator type heaters on a low setting and make sure there is no contact between the moving blanket and the heater. Works for me, YMMV.