I was trying to duplicate a milk paint finish red under black with some of the red iridescence showing through. I followed the article “A Stunning Milk Paint Finish” in the Mar/April 2020 issue.
In order to keep some end grain from showing through I asked the reps at Old Fashioned Milk Paint company if dewaxed shellac would be ok to use as a primer/sealer for this purpose and they agreed – “just let it dry 24hrs”. Also the referenced article above suggested shellac as a layer between the red base and black to prevent dissolving the lower layers and getting a muddy finish.
After sanding HW maple to 220 I applied a 1 lb seal coat followed by 2 coats of red. The red was mixed well and filtered to remove the chunks. I sanded gently between coats. I then buffed out the red a bit and added another coat of shellac before the black as suggested in the article. Test pieces were completed before applying to my practice project. Everything was left to thoroughly dry before the next step.
When I mixed up the black for the final overcoats I made a small wood spatula to chuck into my drill and literally whipped the black. It mixed so well I did not feel the need to filter it. The viscosity was thicker than the paint applied to the test pieces and my test pieces used black that was mixed by hand.
When I applied the black to the test pieces I did not get any red to show through after buffing and shellac. I am wondering if there needs to be a little blending between the layer of red and black that would help to achieve the finish that shows some red? This would be prevented by the shellac sealant layer.
So I just planned to cover with black and not attempt to get the red. The whipped black seemed to go on in a very uniform manner and completely covered the red in one coat which I did not expect.
The next morning the milk paint had cracked down to the base shellac layer taking both red and black layers off with it. The adhesion on my hand mixed test pieces seems fine.
I used a putty knife with a burred edge to remove the milk paint, sanded through the shellac, ordered the binding agent for my next attempt; and will not use shellac.
The only difference is the whipped black seemed to go on thicker and I dried it out in the hot sun (Arizona). Test pieces were dried in AC shop. Could the thicker coating of black contract enough to pull the red layer away from the shellac? Have you seen issues with shellac and milk paint – there seems to be all kinds of opinions out there?
I’m not sure what happened with this approach but any thoughts are appreciated. Sorry for the wordy explanation.
Replies
I will add my 10 cents worth but not an expert - and yes one of many opinions. I have done the black over red milk paint finish many times w/o any real problems, and the red showing thru the black is very stunning effect. Shellac as a seal coat applied to the unfinished piece should not cause a problem provided the mixed shellac isn't too old. I've never applied a coat of shellac over the top of the red "base" coat since you'd have to sand thru the shellac coat in order to reach the red paint, so I agree w/your opinion on this. (The adhesion problems I've experienced w/milk paint have always been between the unfinished piece and the first milk paint coat, not between subsequent milk paint coats). I suspect the cracking occurred because either the black paint was too thick and/or the black paint dried too fast as it was exposed to your hot Arizona sun, which I do believe was the primary cause, particularly since your test pieces didn't crack in your air conditioned space. Good luck.
I’ve used milk paint on two different tool chests. One without any shellac on initial wood or between the red (two coats) and black (two coats). You definitively see more red this way. The other had shellac on the initial wood and then shellac after the two coats of red which then had two coats of black then two coats of linseed oil. Really don’t see the red much this way. All mind dried inside the shop and no issues with paint adherence. Makes me think drying too fast (unless dewaxed shellac was waxed shellac as Zinser sells both). I also thinned the paint to two and half parts of water to one part of solids and used an inexpensive immersion blender I got on Amazon to mix followed by filtering it.
I ended up sanding the maple to 80 grit, no seal coat, and the red just seemed to really grip the wood. completed 3 coats of red and one coat of black followed by laying on some black striping, the paint was much thinner this time which let the red show through more. I sacrificed a milk frother from the kitchen to better mix the paint.
A good experiment overall, next time I will forgo the coat of black texturing (I thought it would buff out more) or really reduce it's application to just let the reddish color show. A darker base wood is probably be a better choice to lessen sand through when buffing out with scotch pads or steel wool. So far I finished with 2 coats of shellac. The base of shellac I used before was zinzer seal coat that was 2 years old so perhaps it was beyond it's shelf life. I also realized my test cutoffs did not receive the same level of finish sanding so they would have provided a better grip for the paint.
Thank you kindly for your inputs!
You didn't need the shellac. Keep it simple.