Water-based Polyurethane over an Oil-based Wiping Stain

      Why does the top finish pull away from the stain coat? Pros explain, and suggest solutions. June 28, 2005

Question
I am using an oil base stain on quarter sawn oak plywood. The process I am using is I sand the plywood with a random orbit sander and 150 grit paper, apply the stain pretty heavily, allow it to dry for a time, and then wipe it off with a clean rag. The pieces dry for about 3 days, but when I go to apply a water-based polyurethane the stain will pull off some sections of the plywood. Is this being caused by me, or is it product failure? I've got a cabinet which I'm scared to put the finish on for fear of the results. Any help would be appreciated.

Forum Responses
(Finishing Forum)
From contributor M:
There are oil stains, and there are Oil stains. Today, most wiping stains are listed as oil stains, and they do not use oil, they use an oily solvent. These stains normally dry in one hour. What may be happening it that a chemical in the WB coating may be re-activating the stain. You may want to try another stain.

You might want to first apply a coat or two of clear shellac. They sell clear Shellac as aerosols, and this is just to seal in the stain. This is common with water base coatings.



From the original questioner:
To contributor M: Thanks for the advice on using shellac, I'll probably end up going that way ultimately. I would like to understand what's going on. I can rub the stain with a clean cloth after a drying period, and nothing comes off. When I apply the finish or wipe the piece down with thinner the stain comes off randomly. Some areas hold up fine, while others lose the stain completely. My first thought was contamination, but there's no rhyme or reason to the stain loss. I also considered that the plywood veneer had somehow glazed over in certain areas.


From Paul Snyder, forum technical advisor:
You should wipe the stain off before it starts to dry. Leaving a lot of stain on the surface is a real weak link in the finish. And some stains can take as long as a couple weeks to dry if you apply them like that. Water-base finishes don't adhere well to uncured oil-base stains.

I'm guessing you're trying to get more color from the stain, and that's why you're leaving it sit for a while before you wipe it off. If so, you have a couple options that will work a lot better; you can dye the wood and then stain it, or dye the wood and then glaze it.

Dye does a great job on oak; you can get it as dark as you want and it will color the wood evenly (no blotching). On quarter-sawn oak, the dye really pops the flecks and rays. But dye doesn't color the pores that well (or not at all), and using a wiping stain or glaze after the dye colors the pores and adds more color overall.

Just to give you an idea, the piece of red oak in the picture has dye on the far left, stain on the far right, and both dye and stain in the middle.




Click here for full size image



From contributor B:
Ive had this happen with oil base finishes too. Back in the day when I was brushing my finishes, if I would over brush an area it would pull some stain out. Are you brushing or spraying? A shellac sealer should solve the problem.


From contributor M:
Some stains contain a binder, and it can be added in the colorant as it is being ground, in other cases it can be added with the solvent. As Contributor P mentioned, wiping stains must be wiped on, then wiped off and allowed to dry.


From contributor D:
I think Contributor P has hit this one dead on. Leaving the stain on long enough to dry, especially on 1/4 sawn oak, leaves a very weak link in your finishing chain. I'm betting that the color pulls off the 1/4 sawn flecks completely. Most wiping stains are designed to color the surface of the wood, more than penetrate into them. By design, they are meant to leave a thin coating on the surface and to impart color to the pours of the wood. The flecks of 1/4 sawn wood have very tight pores, which is why they don't accept stain as dark as the rest of the oak.

I dont think adding a spit coat of shellac will correct this problem. It may increase it, because now you have created a sealed surface where the stain has no ability to bite in. Use the stain as it is designed. Apply it and wipe. Adding a dye before hand will help. You can also apply multiple coats of the same stain, making sure to wait until the previous coat has dried. For oil based finishes, two days is generally enough time between coats. I think that by following this schedule, you should have no problem with the color lifting with the water based topcoat.



From the original questioner:
My confusion comes from the fact that I have already stained and finished 600 square feet of 1/8 inch, 1/4 inch, 3/4 plywood, and solid stock using the same products as I did this time without this sort of trouble. The stain is a Pittsburgh Paint product called Rez Stain and the topcoat is Olympic water base polyurethane. Also, the problem is very random, with sections that are side by side reacting opposite one another. If the shellac seal coat doesn't work, I may be back looking for suggestions on how to strip the piece so I can start over again.


From contributor M:
There is absolutely nothing wrong with using pigmented wiping stains, they may not be as transparent as the dyes, but they certainly have excellent clarity if the stains are wiped dry.
If you are wiping or brushing on the water base over the oil stain, a sprayed on sealer or shellac will lock in the stain, before the brushed or wiped on WB coating.

Another method that you might want to try is to wipe or brush in only one directions, instead of back and forth, then allow the coating to dry. Then apply a second coat in the opposite direct. Allow that to dry, and then you can apply your coatings in you regular method.
This should prevent any stain from coming off.



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