Gun Clogs when Spraying Shellac Primer

It's the nature of the beast, but thinning helps somewhat. September 16, 2008

Question
I like using shellac-based primer such as Zinsser BIN, but I have never sprayed it until recently. The can says it can be sprayed, so I used an HVLP gun, installed a 2.0mm tip/needle, and started spraying. Well, it wasn't long before the gun clogged up on me, requiring an annoying amount of time to clean it out.

So, I tried a Wagner power-painter next. That worked for a while longer, but that eventually clogged up too, even though I was constantly wiping the tip off with alcohol to keep it clear.

So what am I doing wrong? Are there any tips you can share with me? Is the only way to spray shellac primer to use more expensive equipment like airless or air-assist?

Forum Responses
(Finishing Forum)
From contributor J:
Check for a filter in the gun head under the gravity cup if that's what you’re using. It will clog almost instantly, with heavy bodied material. With a 2.0 tip it should be fine.

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From the original questioner:
No, I removed the filter. I almost never use that plastic filter. If I think the finish needs filtered, I use a paper filter as I pour finish into the cup. I think the can said not to thin the BIN, so I didn't. It’s good to know it still works well thinned with alcohol or acetone.

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From contributor A:
I believe the label recommends thinning with mineral spirits to prevent clogging when spraying. I would try Naptha do to its faster evaporation rate.