Strange Brew Trouble Ahead?

A finisher gets a look he likes with a "mish mosh" sequence (latex paint, shellac, waterborne glaze, and clear lacquer). But will the combination perform over time? August 30, 2007

Question
Recently I took some latex paint (Benjamin Moore) and mixed it with some water and floetrol. I sanded a sample maple cabinet door and applied paint wet with a brush. I waited a minute and wiped off. I then let this dry and sprayed a coat of shellac - let that dry. Scuff sanded - applied a water based glaze - let dry. I top-coated with clear lacquer - two coats. Everyone loved the look. I put a sample in my office and a potential customer walked in and said that was the color she wanted. This was all by chance. With this finishing schedule does anyone see a future problem - before I price this job out?

Forum Responses
(Finishing Forum)
From contributor A:
The only problem I see is with the use of shellac as a sealer over latex paint, even though you wipe off the paint. Alcohol and latex are not usually compatible. I would watch for areas of pooling, edges, and raised panel areas. These would be the areas that would fail first. Make a sample of the exact door you would be making for this job and finish using this finish schedule and see what happens.



From contributor B:
It's generally a bad idea to put a hard material such as lacquer over a softer material like latex, even if you seal it. The harder finish is likely to crack.


From contributor C:
You are using sort of a mish mosh of products together, which doesn't mean in this case they won't work successfully, but you could consider other substitutes to get where you are going. It sounds like you are using the latex paint as a stain, wiping off most off it. The ethanol in the shellac is compatible with the latex in the sense that it will dissolve the latex and in this case with the latex being used as a stain rather than a full coating the shellac will bite into it and adhesion should be fine.

The water based glaze over the shellac may be providing a color shift (which you like) as the water would tend to cause blushing of the shellac. Not sure whether this could create a problem over the long term or not. You don't specify the type of lacquer used over the water based glaze but I would want to check for adhesion concerns on that step.

As DCS stated with these products combined you would have to watch for pooling of any areas of the latex which may have been left a bit thicker. All in all it seems that you could easily simplify all concerns by switching some of your materials. An oil stain for the latex with a sealer tinted amber to replace the shellac followed by compatible glaze and top coats. Still, if this works, it works. Just check out that adhesion durability issues won't be a problem and that what you are using won't slow down your processing due to having to be overly cautious on every step.



From contributor D:
I've sprayed Enduro H20 (now GF) over latex paint with no problem and good adhesion. Another option if you want the shellac look is to use Target's H20 shellac and then top it with Target's H20 finishes. You might want to post the question to Jeff at Target's website.


From contributor B:
If I'm going to spray latex for color I perform the following steps:
1- Prime with Zinsser B-I-N
2- Spray on Latex Paint
3- Spray on Emtech 8800 sealer
4- Spray on USL or Emtech 8000

I've never had a problem since the only non WB product is Zinsser. If you keep it compatible it will work just fine and last for years.