Well, I just received an email reply from W&N (that was quick…) My questions to them were:
[INDENT]I presume by the label these varnishes also can be thinned with water? Is there a recommended usage you can share, such as how thin should they be made, and a recommended application method? Can they be used on top of regular oils also, after those oils have properly cured? How is the Artisan Varnish Remover to be used, or more specifically, why would something other than mineral spirits or turpentine not be recommended for these varnishes? Is it okay for me to ask what these varnishes are made of, or what is it that makes them water soluble? Any other information you can offer would be welcomed.[/INDENT]

and their reply follows:
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Dear David-

Thanks for writing to us. Yes, the Artisan Varnishes may be thinned with water. Keep the amount of water less than about 25 percent of the total volume. The same suggestions as applied to traditional oil varnishes apply to the Artisan watermixable oil varnishes.

We recommend varnishing some test pieces first. You’ll get some practice time, and see whether or not you like the look of the varnish sheen. The oil color, whether traditional, or Artisan watermixable oil color, would need to be dry for 6-12 months (depending on paint film thickness) before the varnish is applied.

Two thin coats are better than one thick coat. If you want several layers of varnish but ultimately want a matte or satin sheen, build the thin layers with the Gloss, and finish with the Satin or Matte varnish. This keeps the matting agents in the Satin and Matte varnishes from looking cloudy or hazy, when applied too thickly. Be sure to shake or gently stir the Satin and Matte varnishes before use.

The varnishes may be spray applied with an airbrush, wearing proper respiratory equipment, in a well ventillated area. This application is nice if your work is large scale and/or textured. The varnishes may also be brush applied. A densely packed, synthetic filament brush is a good choice. Our Monarch Glazing brush works nicely:
GLAZING BRUSH – Short Handle

Allow each varnish layer to dry before a new layer is applied (3 hours or more between layers).

The Artisan Varnishes may be applied to traditional oils as well, per the 6-12 month drying time as already mentioned. The formulations for the Artisan Varnishes are proprietary, and as such, even I’m not able to see the ‘ingredient list.’ So, I don’t know what makes the varnishes watersoluble. The main point of the Artisan oil line is to offer a toxic-solvent-free oil painting experience. Therefore, a varnish remover was developed that is solvent free. I don’t know whether or not turpentine or mineral spirits will safely remove the Artisan Varnishes.

The Artisan Varnish Remover is used just like turpentine or mineral spirits would be for traditional oil varnishes. A soft, lint free rag is used to wipe on the varnish remover. Once you see a faint residue of oil color on the rag, the varnish in that area has been completely removed. Avoid heavy pressure or abrasion of the surface during removal.

I’ll share your email with the other Technical Advisors, and if they have any other details to share, I’ll pass them on to you. I’ve also attached an article all about the Artisan Oil series that I trust you’ll find valuable. Thanks for your interest in our art materials.

Kind regards,

Marla Morrison
Technical Advisor
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The attachment she included was the same general information about Artisan that they have on their website.

I’m pleased at her prompt reply. Everything stated sounds like good advice. I’m particularly glad to hear that they can be safely used on any type of oil paint, since I often mix my oil types, which makes me more eager to get some and try it out.

If I get anything further from them I’ll pass it on.