Brendon_t Posted December 19, 2014 Report Share Posted December 19, 2014 It rained here on and off for a few days but hasn't in two days but humidity is still sitting above 70%. Is it absolutely a no go to spray on the shellac when the the humidity is holding this high? Quote Link to comment Share on other sites More sharing options...
Tpt life Posted December 19, 2014 Report Share Posted December 19, 2014 Shellac is in alcohol. I would shoot a test board. Quote Link to comment Share on other sites More sharing options...
Tpt life Posted December 20, 2014 Report Share Posted December 20, 2014 Ok, that sounded smart assy. Let me clarify. It is over 70% for weeks at a time in the summer here and I have good success. Quote Link to comment Share on other sites More sharing options...
Brendon_t Posted December 20, 2014 Author Report Share Posted December 20, 2014 I hit a test board last night dyed the same color, sanded to the same level and it died clear although took about 30 minutes to set up firm. I've never used shellac do I'm not quite sure what would happen if something was wrong. . Quote Link to comment Share on other sites More sharing options...
dwacker Posted December 20, 2014 Report Share Posted December 20, 2014 The reason you don't spray in high humidity is blushing. Doesn't matter if it's WB poly, Shellac or lacquer any fast drying finish can blush. 1 Quote Link to comment Share on other sites More sharing options...
Trip Posted December 20, 2014 Report Share Posted December 20, 2014 70% is very borderline... I'd shoot some test boards... I'd suggest a purpose-made shellac retarder... The purpose-made retarders (NBA) won't be in your local home center -- maybe at the paint store... In a pinch you can use 1oz turpentine per qt -- that's pure gum, not the man-made-crap... If you’re feeling adventurous, you can try 1oz isopropanol (straight drugstore rubbing alcohol) per qt. You can also get some glycol ether (anti-blush) which may be available at your local paint emporium, but don't know it's mixing ratio off the top of my head... Quote Link to comment Share on other sites More sharing options...
Brendon_t Posted December 20, 2014 Author Report Share Posted December 20, 2014 What is blushing? Quote Link to comment Share on other sites More sharing options...
Tpt life Posted December 20, 2014 Report Share Posted December 20, 2014 White haze. Quote Link to comment Share on other sites More sharing options...
Trip Posted December 20, 2014 Report Share Posted December 20, 2014 ==>What is blushing? What happens when you're embarrassed... Or shoot a topcoat when it’s humid and don't use a retarder... Quote Link to comment Share on other sites More sharing options...
wtnhighlander Posted December 20, 2014 Report Share Posted December 20, 2014 I assume blushing is the result of moistute being trappend under the surface if the solvent flashes off quickly, allowing a "crust" to form before the entire film cures out? I've used shellac in 80% - 90% humidity, but never sprayed. I guess blushing doesn't happen with a wipe-on application. Quote Link to comment Share on other sites More sharing options...
dwacker Posted December 20, 2014 Report Share Posted December 20, 2014 Blushing basically is a milky look to your finish. A simple rule of thumb is 65/65 spray above 65 degrees below 65 humidity. BUT the real and accurate way is don't spray if the dew point is not 20 lower than ambient. Quote Link to comment Share on other sites More sharing options...
AceHoleInOne Posted December 20, 2014 Report Share Posted December 20, 2014 Blushing is caused typically on warm days and high humidity. The water in the air is attracted to the cool surface of the fresh finish. Think of it as a cold beer can on a hot day. What happens, the can sweats, same thing with a finish. Because the air is warm, the solvents in the finish flash off faster trapping moisture in thus causing a cloudy finish. -Ace- Quote Link to comment Share on other sites More sharing options...
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