Builders' Forum |
|
| ↓ Scroll to Last Comment ↓ | Forum Guidelines | Builders' Forum |  RSS
|
Epoxy good for high humidity tropics?
Does anybody have experiece with this MAS epoxy in tropical places with high to very high humidity? Will it stay clear even with high humidity in the air?
I built a strip canoe one summer in a garage and much of the epoxying was done during a wet spell. Milky blotching occured in the epoxy as it cured and once out in the sun over the initial months. West System epoxy was used, and shortly after my build they put out a better product that worked well in tropical climates. This was in the mid 90's.
I'll be building in an area with year round high humidities, though not during the depth of the rainy season.
Is the MAS Epoxy in the kit going to be good enough? Will it stay clear? Or should I consider coloring the epoxy or painting inside and out?
3 replies:
RE: Epoxy good for high humidity tropics?
I'm a former Navy weatherman. I think this is what happens.
Water droplets form around microscopic dirt particles in the air. Without those particles, water droplets won't form. The dewpoint is the temperature at which a body of air, when it is cooled, will condense into water droplets.
You lay on your resin late in the day as the temperature is falling to avoid having air bubbles expand in your resin. However, if your kayak cools down to the dewpoint, water will condense on the skin of your kayak, and the microscopic dirt particles in the water droplets may then embed into your resin, clouding it.
I think this will happen regardless of the brand of resin.
Two possible solutions are:
---Use a dehumdifier in your workshop.
---Control the temperature drop so that the room stays above the dewpoint, but not so that the room grows warmer and causes problems with air bubbles.
How do you calculate the dewpoint? We took the air temperature with a matched pair of thermometers, one with a wick on it that we saturated with water, giving us the dry and wet bulb. We then used a rather complicated hand held calculator to give us the dewpoint. Wikepedia has some formulas which look like something out of an advance math class...but they also give this rule of thumb:
"A relative humidity of 100% means dew point is the same as air temp. For 90% RH, dew point is 3 degrees Fahrenheit lower than air temp. For every 10 percent lower, dew point drops 3 °F."
Good luck.
RE: Epoxy good for high humidity tropics?
» Submitted by DavidA - Thu, 8/7/14 » 3:12 PM
as has been detailed in other posts, high humidity can certainly caluse even a non blushing epoxy like MAS to blush. but having said that, it is an issue that can be dealt with. I have had the milky blushing issues using MAS but only when the humidity was high enough to cause a heavy dew overnight. under those circumstances it blushed like crazy.
But absent the heavy dew it generally has been just fine (though I am not in the tropics). My recomendation would be to use MAS since it is better on blush than others, but do not take any chances and always treat it as if it were a blushing epoxy. which only means that you wash it down between each and every coat using a stiff brush or scrub and a little soap with a good rinse (some people say to rinse with water mixed with white vinegar but I havent tried that). do this whether you see the milky stuff or not and you should be fine. pay particular attention to any areas where you encounter a bit of resitance in the brushing as that will indicate the waxy blush that may or may not be visible. after a few strokes you will feel it be cleared away.
This will have the added benefit of making sure that any other contamination issues are not present as well, an issue I have begun to be more and more sensitive to since i am working out in my garage and in retrospect I believe a lot of garage sorts of things probably got onto the boat between coats.
David