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White patches on topcoat HELP!!!

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Forum topic by Konquest posted 03-27-2009 02:53 PM 1356 views 0 times favorited 8 replies Add to Favorites Watch
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Konquest

170 posts in 2909 days


03-27-2009 02:53 PM

I have begun the finishing process on some cabinet doors. They are Shaker style flat panel doors with a glued-in panel of 1/4 veneered plywood. I put one coat of watco cherry danish oil on them and let it sit 2-3 days in a room heated up a bit with an oscillating space heater. I lightly sanded with 600 grit paper, then began applying a topcoat, which was minwax satin polyurethane thinned a bit with mineral spirits. Last night I brushed on a coat and this morning woke up to discover two streaks about 1/2” wide on the panels near the rails and styles on one of the doors. They are cracked, white, and chalky. Seeing as how this is only the first coat, it shoudn’t be a problem to scrape it off and redo the areas where this appeared, however I can’t afford to have this problem pop up again as there is only so much veneer layer that can be sanded. Does anyone have a similar story or knowledge of this kind of problem? Here is what I came up with:
-Contaminated surface (it was in the corners so it probably did not receive as thorough of a sanding)?
-Some thin glue squeeze out that was invisible to the naked eye?
-Contaminated polyurethane (although I successfully coated the back of the doors and the entire cabinet from the same can)?
-Too much heat coming off of the oscillating space heater?
-Too thick of a coat?

Please help as I really don’t want to have to make another door!

-- 9 3/4 fingers remaining.


8 replies so far

View Scott Bryan's profile

Scott Bryan

27251 posts in 3287 days


#1 posted 03-27-2009 03:18 PM

Knoquest, it is hard for me to visualize your problem. Any chance you could post some pictures of the problem that you are describing? If you can that might help. It is possible that the danish oil simply has not cured out. The curing process is dependent upon ambient temperature and “room temperature” is the optimum temperature for the danish oil to cure. But, if this is the case, then the wood surface should still be tacky and it should not produce a “white, chalky appearance”.

Glue spots will show up as white/yellowish areas (if you used a yellow glue) but should not crack the finish. In fact the danish oil and polyurethane are compatible with one another since they are both petroleum based products so there should be not visible interaction between the two products. My best guess is that you are dealing with glue, which may be almost impossible to get off without sanding through the veneer.

-- Challenges are what make life interesting; overcoming them is what makes life meaningful- Joshua Marine

View Konquest's profile

Konquest

170 posts in 2909 days


#2 posted 03-27-2009 03:26 PM

Nah I’m pretty sure the Danish oil is 100% cured. I’ve made that mistake before. I used titebond III. Where the poly cracked and turned white you couldn’t see before. It wasn’t like there was this high-sheen area there. I’ll see about getting a photo or two up before I leave town tonight.

-- 9 3/4 fingers remaining.

View Woodchuck1957's profile

Woodchuck1957

944 posts in 3229 days


#3 posted 03-27-2009 04:08 PM

Personally I don’t understand the use of two different finishes. I don’t know why some people have to make it so difficult.

View Julian's profile

Julian

880 posts in 2991 days


#4 posted 03-27-2009 04:39 PM

The streaks sound like the result of glue that squeezed out between the veneer in the plywood during the manufacturing process. I have had issues with this in plywood from the big box stores.

EDIT:

I just read your last post, and don’t think the glue is the problem. My guess would be an issue with heat since you said that the dual layer finish worked on the rest of the piece. Was the temp any different when you finished the other parts? Oil finishes can take a week to dry completely if the temp isn’t a constant 70 degrees. Another solution is to use a dewaxed shellac over the oil to seal it so the different base and topcoat won’t react with each other.

-- Julian, Park Forest, IL

View Gary's profile

Gary

8968 posts in 2898 days


#5 posted 03-27-2009 04:45 PM

Personally, I don’t understand why some people have the time to be critical yet have no time to be helpful.

-- Gary, DeKalb Texas only 4 miles from the mill

View Peter Oxley's profile

Peter Oxley

1426 posts in 3340 days


#6 posted 03-27-2009 04:52 PM

Sometimes if the space is very warm, the poly will cure too quickly and “blush”. That can cause white streaks or blotches, but I’ve never heard of it cracking.

-- http://www.peteroxley.com -- http://north40studios.etsy.com --

View Konquest's profile

Konquest

170 posts in 2909 days


#7 posted 03-27-2009 05:12 PM

The plywood is not from a big box, it’s from a local lumber dealer/sawmill. The streak isn’t at the seam anyway. Heat could very well be the issue since the panel that was streaked was the absolute closest thing to the heater overnight. The heater blows back and forth like a fan, though. Glue may be the culprit. I use a wet rag to clean up the squeeze out and this streak is right where I would have wiped it near the corner of the panel and frame. The good thing i guess is that if there is glue under the white streaked poly and danish oil, it would only be a microscopic amount that I could hopefully take off without damaging the veneer layer. Also, the veneer layer is thin enough so that the danish oil is probably fully through it, and if I do get the glue off I wouldn’t have to deal with trying to match colors.

-- 9 3/4 fingers remaining.

View PurpLev's profile

PurpLev

8523 posts in 3114 days


#8 posted 03-27-2009 05:32 PM

referring to your last comment – you mention you wipe glue squeeze-out with a wet rag? this could very well smear (a very thin layer of) the glue over your seam as opposed to removing it off of it as you intend to do. Another school of practice is to let the glue partially dry (45 min – the required clamping time) and then when it’s in a semi cured form (outside shell is hard, inside is still a bit gooey) scrap it off with a chisel/blade/scraper. this way, there is no way you’d be smearing any wet glue anywhere as the glue is not wet anymore, and youre not wetting it any further with a damp cloth.

just something to consider.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

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