Blotchy Finish - Woodworking Talk - Woodworkers Forum

 
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post #1 of 19 Old 04-22-2010, 06:00 PM Thread Starter
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Blotchy Finish

About to loose my wooden head!! Applied a 1/3 each mix of oil baseed Polyurethan, BLO, and Mineral spirits to a 3' x 8' white oak table top. First coat left large and small blotchy areas as though nothing adhered to those areas. Followed with three more coats (slow learner) with no better results. Finally applied undiluted poly with a natural bristle brush. DISASTER!! Brush strokes were absolutely unacceptable. Ended up sanding the entire surface to bare wood. Then started over with same 1/3 mix (especially slow learner). No difference - still blotchy. I'm not going a step farther until I get some HELP!!
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post #2 of 19 Old 04-22-2010, 06:05 PM
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PW,

Are you letting conditioner dry overnight then sanding?

Scott
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post #3 of 19 Old 04-22-2010, 06:34 PM
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Check out Charles Neil's blotch video. Click the video player -he's had enough troubled woodworkers over the years pulling their hair out over this problem he's made his own secret formula pre-conditioner available to the public.
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post #4 of 19 Old 04-22-2010, 06:55 PM Thread Starter
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mdntrdr.
If you mean by "conditioner" the 1/3 mix I have used, the answer is yes. I let each coat dry for 24 hours. However, I did not sand between coats. Is that what you recommend? On previous projects I have not used a mix. Used a stain then poly. I sanded between each coat of poly. No problem. This project has baffled me.

TexTim,
Thanks for the tip. I'll check it out.
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post #5 of 19 Old 04-22-2010, 06:59 PM
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Yes,

I apply a heavy coat, let dry overnight, resand then stain.

Scott
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post #6 of 19 Old 04-22-2010, 07:30 PM Thread Starter
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What if I'm not using a stain - just using the BLO, Poly, and Min Spirits? Also, should I use 0000 wool or ?grit sand paper?
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post #7 of 19 Old 04-22-2010, 08:19 PM
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PW,

I missread your post and thought you were using to condition for pre staining.

You are using this as a wipe on finish evidently.

If you are sanded consistantly then I have no idea.

Someone will chime in.

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post #8 of 19 Old 04-22-2010, 09:55 PM
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Do I understand this right? You put a concoction on white oak and you got it to blotch? I've never had white oak blotch in my life. It sounds like you're trying to put on a clear finish. Why not just spray on two coats of a good commercial vinyl sealer, sand to cut the stearates, blow off the powder, and hit the table with a nice alcohol and acetone resistant spray finish. Both Sherwin Williams and Gemini have this product available for prompt.

The entire process can be completed in three hours or less depending on temperature. All testing needs to be done on sample pieces.
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post #9 of 19 Old 04-23-2010, 09:44 AM
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I must agree, i have never seen white oak blotch, I suspect the issue here is more so the mix is not dry, Poly with this much mineral spirits and Blo, will be very slow to dry , while it will appear dry in fact the deep penetration is not, thus you get a wet/dry look, that will appear as blotching, the areas that are softer absorb more , thus remaining wet , the denser areas less and so dry, unless this oak is reclaimed or been around a good while and there is definite areas of the wood itself being drier than others, again it speaks to the varying density within the wood itself , but again the drier areas will soak up more of the mix and appear wetter than the other areas, without seeing the table it is hard to say for certain, but again white oak is not blotch prone, so it has to be a wet dry look, the question is why , there has to be soft /hard areas , for the unequal absorption, oil based anything as well as BLO, will impart a certain amount of color, the natural amber , so if it is heavier in one area than the other , the blotch occurs, again I suspect you are seeing a wet/dry , I would have to see it to know, but i am thinking yo need to let it dry well , this mix you have made is going to carry deep into the wood, it will take more than 24 or 36 hours to dry , it could take a week or two, again its what is absorbed and not the initial surface , once dry wipe it with mineral spirits or naphtha, and see if the blotching continues , it is possible the previous mix once fully dry will have sealed the softer areas and will prevent further blotching, if it still remains then we have to look further to cure the issue .. if i can help email me charles@charlesneilwoodworking.com
and we will see what we can do to cure this .. a couple photos would help alot ...
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post #10 of 19 Old 04-23-2010, 09:54 AM Thread Starter
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Apparently I used the wrong term. Didn't realize "blotching" was actually a surface finishing term. Here's what is happening. After applying the 1/3 mix there are areas that have a nice sheen and areas that remain dull as though nothing has been applied. Admittedly I didn't sand between coats on my initial attempt at finishing this table top (4 coats). Is that where I've gone wrong? If so, what grit is recommended? As I stated in my original post, I have sanded back to bare wood and reapplied only 1 coat of the 1/3 mix so far. I've attached a pic. The darker wood on the sides is red oak and the problem is the same on it. What you see in the pics is dry to hand touch.
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Last edited by PeckerWood; 04-23-2010 at 10:18 AM.
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post #11 of 19 Old 04-23-2010, 11:47 AM
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What I see is a film seperation, meaning im not sure how well BLO and poly mix, it looks to be a case of the 2 inital components seperating , the poly is forming a film on the table and the blo is being absorbed... thus the difference in sheen, if it were me I would let this dry for 3 or 4 days .

then get a good durable oil and be done something like General Finish Arm R Seal or Water Lox , they are as tough as any poly or poly mix you can get... will dry fast and hold up... I must confess I do not understand the mix, BlO is a much weaker finish than poly, mineral spirits just thins it out.... I also cannot see the poly intermixing , its a man made resin base , poly doesnt like to stick to itsself, just cant see it bonding in with BLO , Im not a chemist by any means and could certainly be wrong here... but to me it just doesnt seem like a logical blend..
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post #12 of 19 Old 04-23-2010, 03:29 PM Thread Starter
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Charles,
Thanks for your input. I value that as I know you have many years of experience. Do you recommend that I sand back to bare wood again and then apply the Water Lox? Or should I sand at all?
The 1/3 mix was a suggestion from another woodworker on an earlier post that I did on this site. That's the hazard of asking for advise on a site like this. You can never be sure if the advise is coming from someones experience or just hearsay. This, of course, is not the case with advice proferred by you since you are known for your knowledge of this subject.
I viewed your "blotching" video and found it very informative. Will keep that info in mind for future projects. Thanks for any further advice you might have.
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post #13 of 19 Old 04-23-2010, 04:29 PM
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what I would do is to sand it well, then use a hair drier and warm some spots here and there not hot just toasty, and see if the BLO shows on the surface , if not its dry enough , a good sanding will ensure the poly is abraded to afford adhesion, and open it up as much as possible for the oil to penetrate , be aware that Waterlox has alot of amber to it , so test a scrap first, also do not be surprised if you get a similar look on the first coat of two, because the poly will seal the wood where the BLO doesn't, meaning it can be absorbed at different rates, but after a good overnight dry , either of the oils mentioned will seal and be dry, subsequent coats will build to an equal sheen , and in the case ( because we have so much different stuff here) it doesn't we can fix that as well,
as to your comment, I have been at this for a while now, I am not a fan of BLO , its terrible, in the day when it was actually Boiled it did OK, its still a weak finish,compared to the products we have today, what most are doing is simply adding japan drier to make the stuff dry , its not polymerized like the older stuff, its alot cheaper to throw some drier in it and call it "Boiled" , and its cheap by most finish products, just how I see it, I have some walnut floors in my home, as well as some heart pine ,I have waterlox on the pine and Arm R seal on the walnut .. been down about 5 years now , and I have 2 large dogs, no issues , I also agree forums generate alot of opinions , but its the facts that count and its hard to distinguish the difference ...I refrain from the forums , because while I really enjoy helping folks, I dont have the time to debate, I have made a living all my life doing this, if some one has a question I am always ready and willing to help..and I will tell you what I think, but more so what I "Know", for me the greatest thing is your success.. otherwise im perfectly content to be on the sidelines... my email is above and I will help if I can... never hesitate.. im just like you, just tripped over a few more rocks , that's all... keep me advised... we are on uncertain territory here.. but to clarify, just sand it well.. then lets get it done

Last edited by CharlesNeil; 04-23-2010 at 04:33 PM.
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post #14 of 19 Old 04-23-2010, 06:22 PM Thread Starter
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Charles,
Thanks again for your input. I have obtained some Arm R Seal and will follow your instructions. The present coat of 1/3 has been drying for 3 days. I'll start on this tomorrow. Sure to let you know how this works out.
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post #15 of 19 Old 04-23-2010, 08:13 PM
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I wouldn't think blo and poly would mix well. Burr I've never tried it.
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post #16 of 19 Old 04-24-2010, 10:05 AM
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apply a full wet coat , soak it good, let it sit for 5 or 10 min then wipe it back, let it dry overnight , then scuff sand it with some 400 or finer to defuzz , it shoud be glass smooth , then apply another wet coat , use a foam brush or painters pad, or a good natural hair brush, brush it on thin and wet and as smooth as possible , if it feels too thick add little mineral spirits to thin it a little so it lays out smooth , let it dry overnight then shoot me a picture and lets see where we are at
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post #17 of 19 Old 04-24-2010, 10:32 AM
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A 3 foot by 8 foot top is a big table to be using a wipe on finish. It can be done but if I had to do it and couldn't spray I would use the varnish only thinned with a little mineral spirits and apply with a foam roller.

As soon as it's applied I would tip it off with a foam brush. Dip the brush in the varnish to get it wet and stroke the length of the table with the grain with a very light touch. This will lay out the varnish very nicely, sign painters use this technique to paint gloss signs. (Try on a sample panel until you get the technique down)

The other trick is to make a dust shield for your top to dry under. A 4x8 sheet of cardboard would work great. They use them at the lumber yard on all of their pallets of sheet goods (plywood, mdf etc) Make a simple frame to hold the cardboard to keep it from sagging, have the top on a cart that can be moved under the cardboard or have a friend help you move the carboard over the top after the finish is applied. There should be at least 2-3" of space so air can circulate and allow the finish to dry and still keep the dust out of the finish. This will keep 90% of the dust out of the finish and the rest can be rubbed out with an Abralon pad.

I would use Behlens Rockhard tabletop varnish for this myself if I had to hand apply but the urethane will work if it is a quality product and Rockhard is only available in gloss.

Last edited by Rick Mosher; 04-24-2010 at 10:38 AM.
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post #18 of 19 Old 04-26-2010, 06:55 PM Thread Starter
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Charles,
I followed your instructions and it sure paid off. Used Arm R Seal. So simple I'll probably never use another product for this application. Pics are attached. Can't thank you enough! I have applied 2 coats and intend to apply 3 more.
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post #19 of 19 Old 04-26-2010, 09:55 PM
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Cool,glad you got it handled now.
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