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+-- Thread: Let's talk epoxies.... (/showthread.php?tid=7351630)
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RE: Let's talk epoxies.... - ez-duzit - 12-07-2019
Been using WEST epoxy since the '70's; great product.
As Alan mentioned, you prime the workpieces with neat resin/hardener mix until they won't soak up any more. Solid end grain and plywood edge grain frequently requires many, many coats. Then apply a mixture thickened with either high strength filler or colloidal silica with microfibers; this mixed to the consistency of peanut butter. Cleanup squeeze-out immediately and remove from any surface that will be finished bright. I remove what I can with putty knife and dry paper towel fragments, following up with paper towels wetted with acetone. This minimizes subsequent sanding and preparation time.
Hardener is available in fast, slow and extra slow, which you select based upon ambient temperatures and available working time. There is also a "Special" clear hardener for use in certain coating applications and around potable water systems; this has a different mixing ratio and requires special dispensing pumps.
RE: Let's talk epoxies.... - Alan S - 12-07-2019
(12-06-2019, 11:24 PM)Willyou Wrote: Most epoxies will get quite runny when warm. Warm up the two components before mixing in a bath of hot tap water. You can also warm up the wood piece you are working on with a hot air gun. Start with a slow setting epoxy as the heat will accelerate curing.
Some say that adding a solvent like lacquer thinner will also do it. I'm skeptical. I'm not sure but, I think, it will weaken it.
I agree with Willyou. Be very careful warming up epoxy because as as noted it becomes thinner but also cures faster. Curing releases heat, so it heats up even more. Warming a thin coat to make it soak in works, but I would be wary of warming up anything but a very small container of epoxy. The bigger the container the more problematic because heat is generated throughout, but only lost at the surface. Allowing a fast cure epoxy to harden in a large container can heat it up enough to char, even without adding other heat. Casting resins are quite distinct.
While solvents will thin uncured epoxy, they then need to get out of the cured material. I prefer "100% solids" materials, which mean that even though they start out as liquids, all the components become solid in the cured product without anything needing to evaporate out.
From the System Three line (only because I know about Sys3) their base resin or their Silvertip are reasonably thin. Clear Coat is significantly thinner so it will easily soak into small crevices -- or drip through small nail holes. (Be careful. Another vendor also sells a fine product called Clear Coat, but it's a very different type of epoxy that is not thin.) Even thinner than this, almost like water, is RotFix, designed to soak into punky wood and strengthen it.
Rotfix works, but my favorite use for this epoxy is to make weatherproof knockdown joints in wood. I drill and tap the wood for machine screws, then apply RotFix to the threads. It soaks in, seals and strengthens the threads. After hardening, stainless machine screws can be threaded in without retapping but fit tightly, are very strong and waterproof. It takes a small amount of epoxy for this sort of thing; keeping resin and hardener in a couple of syringes allows very accurate dispensing of the needed small quantities.
RE: Let's talk epoxies.... - KLaz - 12-09-2019
Appreciate all the advice. Always good to have solid information trying something new.
Kris
RE: Let's talk epoxies.... - Cooler - 12-09-2019
Titebond has an "Extend Open Time" glue with 15 minute open time.
https://www.rockler.com/titebond174-and-titebond174-ii-extend-wood-glues-titebond-extend-wood-glue
RE: Let's talk epoxies.... - mstens - 12-09-2019
If all you want is a longer open time, I'd suggest looking at liquid hide glue.
RE: Let's talk epoxies.... - Cooler - 12-09-2019
(12-09-2019, 09:38 AM)mstens Wrote: If all you want is a longer open time, I'd suggest looking at liquid hide glue.
I agree. Hide glue has an open time of about 30 minutes vs. Extended Open Time glue from Titebond (15 minutes) vs. epoxy (Lock-tite lists one version at 60 minutes).
Only the hide glue is reversible however. So you can get a do-over if required.
RE: Let's talk epoxies.... - Jim Waldron - 12-14-2019
(12-06-2019, 06:32 PM)mike4244 Wrote: Dap urea formalahyde glue has a long open time
Urea formaldehyde glue is not gap filling and requires very good tight fitting joints.