[mofo83]

Hello,

I completed an oak dining table about four months ago, which I finished with about six coats of water-base poly. (I fumed the oak, no stain was used.)

After a couple months of use, white "streaks" or "lines" have started to show up on the table top, as you can see in the attached photos. One streak showed up on a glue line, but otherwise they seem to occur at random, though they don't show up on areas of deep grain. Upon close inspection, it looks like there are also long, faint "hairline" cracks in the finish at the same spots as the marks.

A bench I made about a year earlier and finished in the same fashion has not had any such issues.

The marks seem to be occurring only where the table has been used most - we usually only use the "right" end of the table nightly, which is where the marks are showing up. The "left" end has no marks.

I'm guessing it has something to do with water seeping underneath the finish? Maybe it's caused by glasses used without coasters, or from cleaning the tabletop? Or... any other ideas?

The main question is: what can I do now to fix these? I thought maybe I could gently sand these spots and reapply some water based poly... or perhaps I could do a gentle scuff sand and apply an oil based poly to the entire top surface - would that protect it better moving forward?

Thanks for any help!

 

[mdntrdr]

How did you apply the finish? It may be too thick and cracking? :smile:

 

[mofo83]

I applied with a wide brush. I definitely tried not to "slop it on" thick... I would dip just the tip of the brush and always cleaned off any excess. I also did a light scuff sand between coats, then wiped clean with a microfiber cloth.

I wasn't aware that too much thickness could cause problems!

If this is the case, what's the solution? Totally refinishing the top?!

Thanks

 

[mdntrdr]

Yes, there is a recommended mil. thickness not too exceed. I believe the white is moisture possibly trapped in the top or penetrating the surface somehow. I use only solvent based finishes, so I will let the waterborne guys give suggestions on how to fix. :smile:

 

[Rick Mosher]

Is this a solid oak top or veneer?

 

[mofo83]

Solid oak, about an inch thick.

The entire table is solid oak (legs, apron) and these marks don't appear anywhere else.

Also, I'd be a little surprised if the thickness of the finish is the problem. The coats go on so thin, I was even worried that my scuff sanding was taking off most of each coat! It certainly doesn't look very thick either. But I'm certainly no expert.

 

[Steve Neul]

How long after you fumed the wood did you apply the finish? My guess is there is some chemical reaction between the ammonia and the finish. If that is the case I think the white lines might get wider and the finish will start pealing. I would wait a while before doing anything. You might do a lot of work touching it up and then have to take the finish off. If it is only the white lines you could mask off each side of the line and color the white lines with a touch up marker and then put another coat of poly over the top to seal it.

 

[mofo83]

Hmmm... another interesting guess! Thanks.

I think it was actually a quite a log time in between when I fumed the wood and when I applied the finish. Like... months (I stopped working on the table for a long time when my daughter was first born.)

Another clue I just thought of mentioning - the white marks are always parallel to the wood grain.

 

[Old Skhool]

I find that it is curious that you are getting "marks seem to be occurring only where the table has been used most". A second clue seems to be: "Upon close inspection, it looks like there are also long, faint "hairline" cracks in the finish at the same spots as the marks." I am assuming that this part of the table is subject to moisture as you have mentioned. Is it a habit to wipe down this end on the table more often, or more vigorously than the rest? What are you using to clean the table?

For whatever reason, it seems that the finish is breaking down and allowing moisture intrusion in these areas. It is not unheard of for red oak to surface check and you may have/had some very slight checking and not even have seen it. This is more common on thicker stock and can be worsened by improper drying especially KD. (5/4 I assume) Since all the white streaks follow the grain so consistently I think the grain/glue joint has a play in this. The table top is also wider than you benches an is going to experience more expansion and contraction, and the grain itself could be acting on a brittle finish just like a scratch, or score line on glass. As Steve said, some contaminants may have worked their way into these areas prior to finish that caused poor adhesion eventually showing up now.

You may want to list the products that you used and hope that Rick and others can give you advice specific to that finish. I would start with the least aggressive method, rather than jumping into a refinish. I would take one mark and use a pointed scraper to remove the finish in white area. Some very careful sanding with the paper wrapped over a sharp edge to clean and get a base for adhesion. Use a light application of mineral spirits, or water to see if the white is gone. If it is, then I would tape off each side, use an artists brush and use thinned shellac for its ability to bond. Follow up with a coat(s) of the finish you used on the table to level the surface. Remove the tape. (Be sure to allow appropriate drying times between coats.)

If the repair seems to work, and be to your satisfaction I would do the remaining marks. Scuff sanding the top and applying an additional coat may give you back the durability you are looking for without stripping and starting over. I look at it like repainting a car, it is not always necessary to start with bare metal. The same for touching up scratches. Though there are specialty products and methods for this, seems like you may have just the start of a systemic problem, thus the additional coat.

 

[Rick Mosher]

I think the first thing to do is find out if they are just existing cracks that have accumulated water and turned white or if they are checks in the finish that are going to continue. Wood shrinks during the Winter and then Expands again in the Spring and Summer.

I have two suggestions. The first is look through a powerful magnifier and see what they are. Can the white be cleaned out? Then mark the start and end of one with a pencil and see if it is growing or staying the same (Wait maybe a month). If they are stable and not caused by failure from wood movement or just an inferior finish on a table top, You should be able to repair these easily.

 

[Webster]

Possibly it's your scuff coat sanding dust left behind in a groove then finished over.
If that's the case, it shouldn't get any longer or larger.
Can you feel anything when you rub your finger or pull your nail over the white spot? A slight indent?

 

[mofo83]

Thanks for all the great replies!

Let me try to address all the questions.

1. I have the feeling that the white marks do not have to do with checks in the wood. (There ARE some small checks in the ends of two boards, but these do not show up as white marks... they just look like normal little tiny cracks.) But maybe expansion of the wood is causing cracks in the finish?

2. We DO wipe down the side of the table with the marks much more often than the side without marks. I usually just use a slightly dampened paper towel, because I know that using too much water or a harsh cleaner would be bad. We also have water glasses, without coasters (despite my reminders), sitting on the marked end much more often.

3. The marks don't seem to coincide with "grooves" or the deeper areas of grain. In fact, they seem to occur on more "flat" areas. Also, besides the one glue line, the marks seem to coincide with the darker areas of the grain, which is odd (you can see the darker areas of the grain in the photos.)

4.I feel as though I did a pretty thorough job of removing dust after each scuff coat, with multiple passes of a microfiber cloth. But, it's always possible I missed some!

5. When I run my finger over the marks, I can feel the little "hairline crack" in the finish, and I can almost "flake" off the separated finish if I try to. Perhaps I put it on too thin in these areas, somehow?

6. I used only Minwax Polycrylic Satin waterbased finish. Upon further review, I know some people dislike Minwax in general, but it was readily available and a few reviewers said they liked the product. It seems to be working fine on the bench and on the rest of the table, besides the one half of the top, and I like the look of it.

This is the comment that matches most closely with my thoughts:
For whatever reason, it seems that the finish is breaking down and allowing moisture intrusion in these areas. Maybe it is because adhesion was poor in these areas, for whatever reason, or maybe I misapplied the finish in these areas somehow.

I think I will try some of the less intrusive repair methods you all suggested. Or, I was wondering... if I use an artist's brush to apply some more Minwax (or even a different, oil-based finish) to these areas, is it possible that it would also seep into the cracks and "repair" the areas?

Thanks again!

 

[daveinjersey]

FWIW, I've used that finish on a good bit of red oak without ever seeing that problem.

 

[HowardAcheson]

>>>> The entire table is solid oak (legs, apron) and these marks don't appear anywhere else.

That's because only that one area is being wetted and washed. What you are seeing is moisture that has penetrated the finish. It's something that happens with water borne finihes. Waterbornes are not a water and moisture resistant as oil based.

In addition, if you look closely at oil, you will see small lines in the surfaces of the wood. When a finish is applied, the finish does not get deeply into those lines. This allows water and moisture to more easily get into those areas and causes the lines to become more prominent. For oak finishes many finishers will fill the pores of the wood before applying a finish.

It's not good idea to wipe a wood table with a wet rag or sponge. Waterborne finish is not a water and moisture resistant as an oil based finish.

 

[Steve Neul]

Another possibility is if the lines are crevices it's possible that when you wiped off the surface it left sanding dust in the crevice. Sometimes to get all of the dust out it is necessary to use compressed air.

 

[mofo83]

Interesting, thanks for the additional responses.

Before starting this project, I asked a lot of questions on here and it seemed like most people thought that water-based and oil-based finishes weren't all that different as far as durability and water-resistance go.

But, if oil-based is much better with water resistance, should I just do a scuff sand of the existing finish and apply a couple coats of an oil-based poly? Someone else had said that once the water-based finish drys completely, you can apply an oil-based finish on top of it and it should be okay? (Or maybe it's the opposite that's true...!)

Or, if I stick with just fixing the water-based finish, how do I clean it, if a slightly damp paper towel is too wet?

Thanks again.