Troubleshooting Spots in a Wiping Stain and Pre-Cat Finish

This defect could be caused by interaction between the oil stain and the waterborne top coat; or, something might have penetrated through cracks in the top coat. October 26, 2012

Can anyone give me some insight into the spots that are developing in these cherry doors? The doors were stained with a wiping stain, then finished with a water based urethane. In less than 2 years these spots are turning up on the front of the doors, but not the back. I've used this exact same finishing process on 20+ projects and this is the only one I've had a problem with. Is the homeowner using a bad cleaning solution? How can this be fixed?

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Forum Responses
(Finishing Forum)
From contributor J:
I'm guessing some of the stain pooled in the grain and never completely flashed off before the finish was applied. The reservoirs of stain then leached, causing the spots. It's hard to say from the pictures, but it looks like there might be a colorfastness issue as well. Are these doors seeing a lot of sunlight? As for the back of the doors, does the grain detail carry through, or did we catch a slice of the tree where the details are different enough? Additionally, was the same amount of sealer and topcoat applied to the back as the front?

From contributor R:
I would use a magnifying glass and see if you can see checking in the clear coat. Maybe checked clear coat and then a cleaning solution from the customer is leaching in? Just guessing.

From contributor O:
White or whitish spots are from water getting into the finish. That is why you don't see any on the back. Get them to dry real good and recoat while you still can.

From the original questioner:
I don't think the stain pooling in the middle of the doors in almost every door in the kitchen is the most likely cause, but a possibility. This would be more likely where the center panel meets the frame. What do you mean by colorfastness? The kitchen has a southern exposure and does see a lot of indirect sunlight.

Thanks for the help. Please offer more ideas.

There is a section of cabinetry separate from the rest of the cabinetry (yet in the same room) that does not show any sign of this. There is also the peninsula back that was finished at another time, that shows signs of the spotting. These facts, along with the back of the doors showing no sign of this, leads me to think something is being put on the front of the cabinetry that is causing this. What could it be?

From contributor A:
The customer or their maid probably hosed the doors down with Pledge or some other furniture polish. Maybe lemon oil, who knows? What difference does it really make? Are you going to fix it or not? Because you'll have a hell of a time shading those doors to match the rest of the job if you strip and sand them. I would think this one is on the customer, not you.

From contributor V:
Looks to me that the finish has opened and a cleaner that is caustic has reached the wood. Micro-cracks.

From contributor J:
Color fastness is basically the ability of a product to resist changing color when exposed to light. Linseed oil, for example, is photochemically reactive and darkens with light exposure. Aniline dyes, for example, are not color fast.

Are we talking about the dark spots, or the foggy streaks which could be from camera flash or bad lighting? If it's the dark spots, then what type of stain did you use - waterbased, solvent based, etc.? What was the flash off period between stain and your first seal coat?

From the original questioner:
Thanks for the response. We're talking about the dark spots. I think the foggy streaks are mostly from poor lighting and phone camera. The stain used was solvent based and the time between wiping the stain and spraying the finish would have been at least 12 hours. I usually stain one day, then spray the next.

I am trying to gain some knowledge about what may have happened before I try to fix anything. I don't want to accuse her of anything when it could be entirely my fault. How should I fix this? Chemicals? Sand it down to nothing? The common theme is that something is getting behind the finish and bleeding.

From contributor U:
Where are these in relation to sources of moisture, windows, uppers and lowers, or just one section? Please give more info on everything - even the flooring these cabinets are sitting on.

From contributor J:
Does the topcoat itself look and feel intact? Are the other spots consistent with the grain characteristics? (For example did it occur in both the sap and heartwood?) I ask this because there seems to be no spotting in your door frame.

From the original questioner:
How did the micro-cracks develop? Is it my fault? Or from a cleaning solution? Or from an abrasive cloth/rag?

The finish seems to be fine. Nothing noticeable to the naked eye, feels normal. I see what you mean by no spotting in the door frame, but while in the home I don't recall thinking "strange, it's only the center panel." I think it's a coincidence of the particular photo. The spotting was on an end panel finished at another time than the doors.

What I'm trying to hone in on is: Do I have any financial responsibility here? I want to fix this, but is it my duty to pay for it? Or is it hers, because it's her fault? Also, what is the best way to fix it? Sand to bare wood? Chemicals?

From contributor A:
What brand of stain did you use, and was it an oil based or a water based stain? How did you apply it, how long before you topcoated it, and what was the topcoat you used? Manufacturer and product name. Then give us your finish schedule please.

From contributor J:
The solvent based stain - was it an oil based product or some other ketone blend? Was the stain a stock color?

As far as ownership of the problem, I am inclined to think that it is yours, for the following reasons:
1) The spots appear to have formed from behind the finish.
2) Because the finish seems intact, it is unlikely that your client caused a compromise in integrity.
3) If it is micro-cracks, it is more likely application than some mysterious cleaning product applied by the client.

Back to diagnostics... There is some common denominator that you haven't identified yet, and this is important, because when you fix it, you don't want to repeat it.

From the original questioner:
Stain - Sherwin Williams Sherwood wiping stain, oil based - Cherry
Finish - General Finishes Water Based Pre-Cat Urethane

I stain the doors one day, and finish the next. I have used this combination of wood, stain, and finish a dozen times over the last 4 years. I haven't had any problems.

From contributor A:
If I had to pick a cause based on the information provided I would say the stain was not fully cured and migrated out into the coating. I have seen that very thing happen at a shop I used to work at where they used oil based wiping stains and WB topcoats. And you are right. Not every job had a failure, but some did.

The key is the oil in the stain needs to be fully and completely cured before the topcoat is applied. Heat, humidity, temp and the amount of stain left on the wood as well as the depth of the pores all have a factor in the drying rate.

If we were to use an oil stain under a WB topcoat I would require a minimum of 48 hours of time before I would coat it. You may be able to go faster but then again you may be rolling the dice.

From contributor J:
Kinda back where we started from... Often stain, particularly oil base, kind of finds its way into wood cells. It seems to have dried and flashed off, but in reality there it is hiding. The fact that you have gotten away with it in the past is pure happenstance. Sometimes it will dry in the wood and never rear its presence, as it may dry out where it is.

Contributor O has concurred with this diagnostic and given you the best prevention in the future with this stain - more time before you top coat.

As for your remedy for this existing kitchen problem. That's dependent on your skill level. The simplest would be to sand off the topcoat with whatever grit you used just prior to staining, blend the stain as required, re-topcoat, and give yourself time, not only for curing, but to figure out your methodology. If the job isn't too far a distance, you might want to start with a pair of doors.

From the original questioner:
Damn. This is not good news. Thanks for your help.

From contributor A:
The best advice I can give you is to make the switch to GF stains to go along with their topcoats. Then you will have a superior system and eliminate the potential headaches of waterborne/oil compatibility. Then I would recommend testing their poly and Endurovar as, in my opinion, they are both better than the pre-cat.

From contributor B:
Are you saying that you do have micro-cracks? If that's the case, you could have anything behind the finish - cleaning solvent, water, etc. I had micro-cracks once when I used Target em2000 CV over GF sanding sealer years ago. It took about a year to fail. I sanded it down (gently), let it sit for a few days to let whatever moisture dry out, and then restained, barrier coated with seal cote (dewaxed) and the 2 coats SS and TC with GF pre-cat. I had to do all of the lower cabs to make it blend.

You don't say what your schedule is for your finish. How many coats of pre-cat are you using? Do you seal with SS? How many coats? In the future if you use oil stains, 48 hours is minimum (bone dry) and I would barrier coat with dewaxed seal cote and then at least 2 coats of GFs SS (I use 3 coats of SS) then TC with the pre-cat. Better yet, go with GF's or, for that matter, any other WB staining/dye system. Stain and start finishing the same day.

From contributor B:
Micro-cracks can be seen with a magnifying glass, or put some white flour on a small section - the flour will get into any cracks like sanding dust. Too-thin-finish cracks will generally be longitudinal cracks, as opposed to crazing, like with a compatibility issue (oil stain-WB finish).

My gut instinct tells me the finish in some way has failed. Either adhesion issues (stain 2 WB finish), or too thin finish and aggressive cleaning, which could lead to a break down and leaching of cleaning solvents/liquids underneath.