PSA: Stop overfilling your primer gun cup

Did this for years. Always filled it to the brim. Thought I was saving time on refills. Last week my buddy Dave watched me spray a bumper and said "you know that's why you're getting runs, right?" He was right. Half full gives way better control. Has anyone else had a simple habit change fix their paint work?

3 comments

3 Comments

the_rowan6d ago

Toss that primer cup fill habit in the trash, seriously. The overspill messes with the siphon tube's balance and makes the gun spit unevenly. I'd add that keeping it half full also prevents that nasty suction drag where the tail of the mix pulls air instead of paint. It's a weird small change but it fixes both runs AND tip dry issues at the same time. Glad Dave called you out, sometimes we need that friendly wake up call.

thomas.river6d ago

Yeah, the suction drag thing is real. I used to overfill all the time and got that same spitting issue where the gun would just start coughing halfway through a pass. Half full really is the sweet spot, I started doing it on my last job and it saved a ton of cleanup time too. The overspill mess is a pain to wipe off the lid every time you set it down. Glad I'm not the only one who learned this the hard way.

cora8136d ago

My dad does the same thing with the gas tank on his mower, fills it right to the brim every time and wonders why it sputters on hills. That same logic of leaving a little room for air to move applies to paint guns, fuel systems, probably a dozen other tools too. People just default to filling things all the way because it feels right, but the half full rule usually beats it.