Sealer before waterbased poly?

I just got a new LVLP sprayer (read NEWBIE) and plan on spraying some shop cabinets with WB poly (leaning toward one of the Target or General Finish products). I have spent several hours looking through posts on this forum and see that many people spray a thin coat of shellac (to seal the grain I think) before spraying the WB coats. Is a shellac sealer really necessary or will most of the WB polys also seal the grain? Second, if I use shellac, can I use either alcohol or WB shellac? Finally, can standard alcohol based shellac be sprayed without an explosion proof fan? Thanks for you help.

The Water-borne finish will seal the wood. However, it will leave the wood very pale the shellac help reduce the amount of raised grain from the waterborne finish; it also adds a nice straw color. WB shellac is a waste of time, material and money. Alcohol fumes are not nearly as combustible as nitro cellulous lacquer fumes. I've sprayed for many years without special fans. You do need to PROTECT YOUR LUNGS! I know people that have sprayed shellac and ended up VERY DRUNK. Breathing in the alcohol fumes is said to be the fastest and worst drunk ever. Goes from your lungs straight to your blood.

What Scott said, with one exception. I've been drunk on shellac fumes, and I've been drunk on oil-based primer fumes. The oil-based fumes were much, much worse because they gave me more of a "dirty" buzz, with some nausea (I even had to stick around work a couple more hours to sober up because there was no way I could drive home).

I agree with Scott about the Waterborne shellac being not a great idea. I would add that the shellac chosen to go under waterborne poly should be both dewaxed and fresh. Freshness is particularly important for the one pre-mixed dewaxed shellac which is SealCoat. It's a good idea to mix from flakes so you KNOW it is fresh.

I spray a lot of WB products and often spray a coat of Sealcoat shellac first for the very reasons Scott mentioned, color and prevention of grain raising. I spray indoors in a temporary spray booth which I exhaust with the fan of my dust collector out an open window. I think the combustion point of alcohol is something like 11%, and there's just no way to get it that high spraying 7 cfm when the fan draws 1100 cfm. I wouldn't spray much of either shellac or WB products w/o some type of exhaust. And I always wear an organics respirator. (Note: I would never spray solvent based products (other than shellac) with my setup.) Also, I've never used Target's products, but I've sprayed quite a lot of GF's High Perf. Poly, EnduroVar, and Enduro Clear Poly. They all spray well, with the HP Poly being the easiest for me.

John

I would second the recommendation of mixing your own dewaxed shellac. Target coatings says not to use sealcoat under its finishes since some people have had problems. They seem to say it is from too thick a coat and that sealcoat is more acidic than the stuff you mix and can cause problems.
Tom

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Originally Posted by Thomas S Stockton

I would second the recommendation of mixing your own dewaxed shellac. Target coatings says not to use sealcoat under its finishes since some people have had problems. They seem to say it is from too thick a coat and that sealcoat is more acidic than the stuff you mix and can cause problems.
Tom

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Interesting, I've never heard that. I always thought that dewaxed shellac was the universal sealer. Sealcoat has always worked well for me - with GF products anyway. It's just so easy to go buy a can that's all premixed, and always works. GF cautions not to apply too thick a layer of shellac (no mention of what type) under their EnduroVar, so maybe this is consistent with what Target is saying. I've shot a fair amount of EnduroVar over a coat of Sealcoat, however, with no adhesion problems yet.

John

GF Enduro has a WB sanding sealer which is easy to level (easier to sand than topcoats). In my experience it dries in about an hour or less(dry conditions) ready for next coat of sanding sealer if you need more build to level, or first coat of your finish.

Very helpful information, thanks guys. I do have shellac flakes so I can mix it fresh, and will shortly have a spray booth. What weight would you recommend for the sealer coat, 1#? 2#? Also, any recommendation for the best Target and GF finishes for durability on shop cabinets.

I use this technique a lot, but it's not to "seal the wood". Rather, it's to seal the water soluble dye I use and/or to create a barrier coat between oil (typically BLO) and my water-borne top coats. (I use Target EM6000 most of the time) I personally have not had an issue using SealCoat, but I also spray it and it's never very thick...just enough to seal and provide a little amber. Mixing one's own is the best, but in the interest of the limited time I have and the long intervals between projects, I've opted to just use the SealCoat.