Solvent-Borne Stains with Water-Borne Top Coats

      A question about a tricky finishing challenge leads to a discussion of staining, glazing, and toning techniques. December 29, 2008

Question
I have been HVLP spraying WB lacquer for a while with success, but now when trying to do more dark staining, I've been having problems with adhesion of the topcoats. A current job has me staining alder very dark ("espresso"), almost opaque. I'm currently trying Gemini WB products. First I put on a red mahogany Gemini dye stain, then a black solvent-based Gemini stain. Then Gemini WB satin topcoats.

I had reservations about using the solvent-based stain, but was reassured by my supplier that the solvent-based stain would be okay under the WB topcoats, as long as it was dry. I now have some peeling problems.

I was wondering what my staining schedule should be to build up a very dark, opaque color. I want to avoid shading (putting color in the topcoats) but wonder if it is possible to avoid it. How can I build up a very dark color without having adhesion problems?

Forum Responses
(Finishing Forum)
From contributor R:
What was the length of time between the last coat of stain and the first coat of waterborne lacquer? Adhesion problems most often develop when the solvent borne stain has not thoroughly dried before commencing with the water topcoat. I usually wait overnight before putting on a topcoat of ML Campbell's Aqualente, on top of their acetone-based Woodsong Stains. The longer you wait between stain and finish (at least for what you are doing), the better the chance becomes that the waterborne topcoat will adhere properly. So states my MLC rep. I personally don't like to wait... What type of wood is on this project?



From contributor P:
Dewaxed shellac (Zinsser Seal Coat), over the stain, before your topcoats, should solve your problem.


From the original questioner:
For this project, alder. My Gemini rep said the stain would dry in 1-2 hours, but I left it overnight. I'm actually using the stain as a glaze over the last WB topcoats. The stain wasn't dark enough for the customer, so I am glazing over, scuff sanded the surface first, applied more black solvent-based stain, waited overnight. I'll probably spray this afternoon.

I've used dewaxed shellac a lot. What application is best? I usually wipe it on, but I usually end up wiping off some of the stain. That is why I'm trying to avoid using it. Thanks!



From contributor P:
Spray the Seal Coat. You just need a very light application to lock down the stain. Give it 30 minutes to dry, scuff sand and you're ready to topcoat.

I haven't used the Gemini products, so test first. Is the Gemini stain oil-based, or a fast-drying solvent? If it's oil-based, I'd give it 48 hours to dry before the Seal Coat. If it's alcohol-based, be careful with the Seal Coat, as it's alcohol-based, too, and a too-heavy application might reactivate the stain.



From contributor J:
It sounds like you may be trying to get too much color with the black stain... Multiple coats or even just thick coats of pigment stains can cause adhesion problems even with solvent based topcoats.

Drying is an issue of course, but if your stain is applied too heavy, no amount of dry time will be sufficient to keep the excess pigments from blocking adhesion of your seal/top coats to the wood underneath.

You are on the right track starting off with a dye stain. Unlike pigment stains, dyes can be applied in almost endless coats to build color when done correctly. Maybe you should try a darker red dye or even a coat of black dye before applying the black wiping stain?



From contributor J:
I forgot to add: Using a solvent stain as a glaze in between coats of WB may not be the best idea either...


From the original questioner:
Thanks. The stain is oil-based so I will wait until tomorrow to spray. Isn't there a quicker way to do this? Two days' wait for every stain coat will be challenging (with other projects waiting around to be worked on/stored). My dilemma is getting that opaque dark brown or other color. Dyes are good but sometimes I need the wood grain to be muted a bit more. The dye sometimes gives it too much depth. I'm trying to get that almost painted look, but with some wood accents underneath. Is this sprayed on in layers (shading)? Can I do it without tinting the WB lacquer topcoats, or is that how you get that dark color?

That's what the Gemini rep said would work, to just let the solvent-based stain dry and spray the WB right over it.



From contributor J:
What do you have against tinting your topcoats? This is very easy to do when you get used to it. 896 colorants should do the trick, but a little sample work is always necessary.


From contributor P:
You're right. I totally missed that in the questioner's second post. It's usually not a good idea to apply stains over a topcoat. A toner would be better. TransTint dye added to your topcoat is a good way to adjust the color after the fact.


From the original questioner:
Isn't that what is done when glazing using solvent-based finishes? Is there a glazing method when using WB finishes, or a special product that can be used for this, or is it just not a good idea and I should use toner only? My reservations for toning are that an even color distribution is harder to get (with overlap of the fan when spraying, sometimes the corners will get more color).


From contributor J:
I can't speak in regard to Gemini products specifically, but in general, use a glaze as a glaze. Sure, there are some stains where it will work and some that even work very well in this regard, but not all stains are made the same way and some will cause major problems, especially with water based. Remember that when you use all solvent base products, you will usually get some degree of solvent bite that does not happen with WB products. There are some companies out there that do make water based glazes.

Making a shading finish in your sealer and/or topcoat should be nothing to shy away from. The trick is getting your mixture correct. Don't try to make it too strong; making it weaker and building the color in multiple coats makes it more forgiving. The right equipment and spraying techniques will help too.

Build your skill with toners/shading finishes over time. Start by incorporating the use of a weakly colored finish as only a part of the overall color, and then you can gradually try more difficult processes. Water soluble dyes have better clarity than pigments and are easier to avoid the painted look.



From contributor P:
The definitions of glazing and toning can get a little fuzzy, I'll admit. Usually a glaze is a product made specifically for glazing, whether water or oil-based. Stains are not typically meant to be used as glazes, but people use them for that purpose successfully, most often oil-based gel stains. The problem with using a stain over a cured topcoat is that it won't bite into the topcoat enough to provide good adhesion.

There are decent WB glazes. I use Golden Products glazes to do "antiquing," where the glaze is brushed on, then wiped off, but hangs up in the profiles (of a moulding for example). For overall color manipulation, I use toning. It does take a little practice and care to spray it evenly, but it's not super difficult if you follow your normal good spraying practices for overlapping. If you're nervous about that, you can sneak up on your final color by doing multiple passes with less color added to your topcoat.



From the original questioner:
Thanks for all the input. I'm going to focus more on the dye stain (more bite) and toner in the topcoats when staining. Samples, samples, samples.


From contributor I:
We have done several of these jobs in lyptus, alder and cherry. You need to find yourself an ICA distributor and order the CNA stain kit. We use this stain exclusively and get excellent results.


From contributor F:
The advice above to start out dark, even black, is the way to go. I have had to make this West Elm chocolate brown several times. I found the best method is:
- Washcoat the piece with 1/2# dewaxed shellac.
- Spray 2 coats of a black solvent-based dye stain.
- Washcoat the piece with 1# or 1/2# dewaxed shellac to "lock" the dye.
- Use a chocolate brown or red-brown oil-based gel stain over the entire piece to warm it up and give it that espresso brown tone.
- Let that dry overnight, then spray another barrier coat of 1# shellac, followed by whatever topcoat you wish.

In summary, black with a brown overtone is much easier than trying to darken things later. The shellac coats and the dye staining can be done in a single day, with the only wait being for the gel stain to dry 24 hours or so. I am always amazed by how dark customers want their furniture.



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