Wednesday, March 19, 2014

Curing oven

Ever want to speed up epoxy hardening?  Or 5200?  Because time is money, manufacturers use curing ovens to save time.  But how can the savvy boater do it?  Are we doomed forever to wait for the slow cure?  Over at Sail Delmarva Drew has an answer.
Numerous times I have post-cured epoxy projects or hurried alone some small painted object by placing it in the kitchen oven set to "warm." The object would be dry already, but probably not so well cured as I would like by the weekend, and a few hours at 150F can work wonders, reducing chipping on new paint and bringing epoxy to full strength. It always causes a little disruption to havea project in the oven.

Another common problem, at least for northern sailors, is to get polyurethane adhesives and caulks to cure in the winter. Even if we take them inside where it's warm, they just don't cure. The problems is that polyurethanes require moisture to cure, just as epoxy requires a "part b," and a heated home is desert dry, the RH typically below 40%.

When I started to repair the exploded hiking boots with polyurethane adhesive, particularly because of the thick application. I knew I would need a very warm humid cure. Because om my work with mold and mildew for Practical Sailor, the solution was obvious.

A heating pad on medium seemed about right, but it has 3 settings. Generally it is better to have a gel cure before going in; the higher temperatures can make paint and epoxy sag.

If humidity is required, add a damp towel.

Bingo. By adding humidity, sealants like 3M 5200 can be pushed in 12-36 hours instead of a week or more. If dry curing is the goal, skip the damp towel. In the photo I had polyurethane coated some straps, but only in the center for wear resistance; by trapping them in the lid they don't touch anything and were cured in the morning.

If some things are so bloody obvious, why does it take us so long to figure them out?

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