The Stovebolt Site Forums The Shop Area Paint and Body Shop Humidity and sandblasting

Trying to get my frame sandblasted and painted. What humidity level is too high to sandblast? Would like to know a benchmark for what is too high without finding out the hard way by clogging up my blaster due to high humidity...

Located in central Texas. Should have done this during the summer when the rain was no where to be found. Now it wants to rain every day. Trying to find a two day stretch when I can blast and coat with epoxy.

Jon,

If you don't have a very sophisticated air dying system, moisture will most likely clog up the nozzle. My low tech rudimentary gravity sand blast system will clog up badly when the RH is 60% or higher. In your humid part of the world, low RH days are hard to find but you should have some "window" of opportunity in the spring and fall. I would suggest that you hunt for a window of lower RH that could be found right after a frontal system passes. Look at the National Weather Service hourly weather graph of your particular geographic area to determine when the lowest humidity of the day will occur (typically in mid-late afternoon). Good luck, it is a messy thankless job but the outcome is worth the effort!

https://www.weather.gov/wrn/hourly-weather-graph

Paul

Hi, Jon. I've found even 50% RH may be too high. As Paul says it depends on your system but the more low-tech it is, the less humidity it will take to clog it. Usually there will be days between Thanksgiving and Christmas where it is sunny and dry with RH down to 25~30%. Those are the ones you want. Right now is like a swamp in North and Central TX. You have a sand hood, yes? Good luck.

It's a pressurized pot system. I have a hood that came with it, but its pretty beat up. Last stuff I sanded I just used a face shield, ear muffs, and a respirator.

I sandblasted some front end parts (fender braces, radiator shroud, etc) on a nice low RH day. But my epoxy was old and had set up on me. Otherwise I would have hammered down on the frame, which is what I need to get finished up first. A couple of good days have come and gone but calls for rain the next day and didn't want to get rain/moisture on a freshly epoxied frame before it has had its full window to cure. Having to do it all outside on the frame.

That's a pretty slick resource Paul, thanks for posting.

Winter sandblasting below freezing is excellent but be sure to blow out your lines and drain your compressor right after. Even with professional equipment water in the air is always a consideration. A good air dryer is important even for a small home blast cabinet.

A friend made his own sandblaster with a pressure washer and a venturi mixer. He was also using a rust inhibitor to prevent flash rust. Looked messy compared to dry blasting but necessity is the mother of invention they say.