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Grain filling (Read 461 times)
 
Bruce Kamp
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Grain filling
Dec 12th, 2016 at 12:05pm
 
My finish of choice at the moment is sometimes sanding sealer first, depending on the wood. Then I usually apply one of the colors of danish oil. I let that cure for a few days and then apply a thinned oil based poly. After the last coat of thinned poly I let it cure for about a week. Then I use rottonstone to achieve the luster I want. I am usually shooting for a sheen leaning more towards satin.
I understand that there are MANY opinions out there on this topic and that many will not agree with my approach. However, I feel that I am evolving and am eager to learn better ways.
The specific question I have here has to do with grain filling. Take oak as an example. I have been reading about using the sanding process to create a slurry that then fills the grain. I have seen sanding with 100 grit using sanding sealer as the lubricant. However, it seems SS dries fast, maybe too fast, to be effective at this. Is there any difference in using, say, Deft lacquer based vs Deft oil bases SS for this? How will this affect what final finish I can use?
I have also read about using the danish oil as the lube. Apply it then sand with 100 grit until I get a slurry then let dry and sand before applying final finish.
I am shooting for a smooth finish on the oak. I have not tried lacquer yet as I am trying for a more durable finish.
I have read some books on finishing by Bob Flexner and maybe need to go back and reread them. I was hoping to get an answer here on this one aspect, grain filling.
Thank you
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Ed Weber
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Re: Grain filling
Reply #1 - Dec 12th, 2016 at 2:03pm
 
Bruce, here are two articles that cover the application and use of sanding sealers and fillers. They explain it better than I think I could.
IMO, It's a personal preference, the vast majority of the time it is not needed.. Very seldom does the wood require you to use a sealer. Some naturally oily tropical species may require a sealer for better finish adhesion.
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« Last Edit: Dec 12th, 2016 at 2:05pm by Ed Weber »  
 
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Don Stephan
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Re: Grain filling
Reply #2 - Dec 12th, 2016 at 7:44pm
 
Bruce

Ed provided links to two easy to read articles.  What you will find when you read them is that they seem to be written essentially for flat surfaces, not turned ones.

Sanding Sealers were developed for the production finishing business, so they will dry very quickly.

100 grit sounds extremely course for trying to create a sanding slurry.  The sanding scratches may be very noticeable in the final product. 

Oak has such large pores that I'm not sure there is an easy way to produce a filled pore finish on turned pieces.  On flat work finishers might use an oil based pore filler, but they likely would require two applications on oak, and dry hard.  I'm not sure a Danish oil sanding slurry would fill oak pores even with two go-rounds.

You might consider experimenting first on some flat boards.
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Ed Weber
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Re: Grain filling
Reply #3 - Dec 12th, 2016 at 8:36pm
 
Don, you;re correct.
Not everything translates well from flat woodworking to turning.
Don Stephan wrote on Dec 12th, 2016 at 7:44pm:
Oak has such large pores that I'm not sure there is an easy way to produce a filled pore finish on turned pieces.

I have seen one person use a slow turn and epoxy method of coating pieces with voids and open grain but this is somewhat specialized (not for everyone)

Bruce, there are usually two ways to go about filling grain.
1. One very thick coat of finish that will fill all the voids in the grain and self level over the entire piece.
2. Multiple coats that get sanded after each application, which in turn gradually raise the level of the void or grain to even with the rest of the surface.
Number two is "usually" the route to go for a turned piece as I mentioned above.
Making a slurry to be used as a grain filler can potentially leave a less than desirable finish. Finish and sanding abrasive may fill the grain but may also leave you with a "dull looking" final result.
Bruce, you're correct, everyone seems to have a "special" method for finishing a piece. Just remember, it's the final result that counts. If the finish looks and performs the way you want, how you got there is up to you.
Personally I do not/will not use a sanding slurry that will be part of the finish.
I agree with Don's suggestion of experimenting
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Bruce Kamp
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Re: Grain filling
Reply #4 - Dec 13th, 2016 at 12:08am
 
Thank you guys. What you say makes sense. I have had some luck with applying the poly, after using sanding sealer, and then letting the piece turn. I can get my lathe down to 55 rpm. I let it turn for 15 minutes , or so. That seems to help with the leveling. I haven't yet tried  a thicker coat with this method. I usually used thinned. I might experiment with a thicker coat to see if Ed's #1 might work. When I have tried to level after a number of thin coats I usually end up going through the finish trying to get it smooth down to the filled pores.
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Ed Weber
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Re: Grain filling
Reply #5 - Dec 13th, 2016 at 10:05am
 
Bruce Kamp wrote on Dec 13th, 2016 at 12:08am:
I have had some luck with applying the poly, after using sanding sealer, and then letting the piece turn. I can get my lathe down to 55 rpm. I let it turn for 15 minutes , or so. That seems to help with the leveling. I haven't yet tried  a thicker coat with this method.


I usually don't feel the need to "thin" my finishes, especially if there is sanding sealer already applied, what would be the point. Once the sealer is applied and leaves you with a good base to start with, there should be no need to alter the finish at all.
A slow turn with out of the can viscosity usually works fine but you will need to sand in between coats until the grain reaches the level you want. You can only apply so much at a time before the finish will begin to form curtains and/or drips.
Some polyurethanes are thicker than others and there are dozens to choose from. Ambient temperature also comes into play when trying to apply a "thicker" than normal coat.
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Bruce Kamp
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Re: Grain filling
Reply #6 - Dec 13th, 2016 at 11:58am
 
My reason for thinning has always been to achieve leveling/eliminate brush/rag strokes. I have also adhered to the "many thin coats vs one or two thick coats is better" advice. Maybe I can start to use unthinned poly with a slow turn. It would then seem to allow me to speed up the finishing process. Although it would seem that it might take a bit more time  to dry.
Thanks again for all the good advice.
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Don Stephan
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Re: Grain filling
Reply #7 - Dec 13th, 2016 at 3:47pm
 
Seems I've read before a recommendation to sand between coats of polyurethane to give each new coat a mechanical connection to the prior one.  Not sue if thinned coats would adhere to each other without light sanding.

Sanding through when leveling can be frustrating when a stain has been applied.  Some finishes may shrink for several days, which would require longer wait time before level sanding.

I agree that brush strokes on a piece on the lathe would be frustrating as well.  Are you bound and determined to use poly?  If not, what are your objectives for the finish?
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Ed Weber
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Re: Grain filling
Reply #8 - Dec 13th, 2016 at 6:40pm
 
Don Stephan wrote on Dec 13th, 2016 at 3:47pm:
Seems I've read before a recommendation to sand between coats of polyurethane to give each new coat a mechanical connection to the prior one.  Not sue if thinned coats would adhere to each other without light sanding.


"Once a myth gets into print, it’s common for it to be repeated endlessly until it becomes “fact,” simply because everyone says it. " –Bob Flexner

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