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End grain (Read 271 times)
 
Frank Padden
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End grain
Aug 27th, 2017 at 3:22pm
 
This has probably been discussed but I'll ask again. After I work my way up to 400 grit, sometimes it looks as though the finer sawdust is trapped in the endgrain and I have to start over again with 80 or 100 grit. It's usually the same area that doesn't want to take whatever finish I am using. Any ideas? Thanks, Frank
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Ed Weber
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Re: End grain
Reply #1 - Aug 27th, 2017 at 4:51pm
 
I think I know what you mean, but if you could post a photo it would help.

I always use compressed (usually between grits) and flush off my sanding debris with mineral spirits.
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Don Stephan
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Re: End grain
Reply #2 - Aug 27th, 2017 at 5:48pm
 
Frank

I'm not sure either, but will say that defects (scratches, fine tearout) sometimes are highlighted by sanding dust when I get to about 400 grit but not before.  Apparently coarser sanding dust doesn't get trapped and/or packed down?

Not sure what you mean by the wood not taking finish - for me, missed tearout takes finish the same as smooth wood, but looks different because of the irregular surface.
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Frank Padden
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Re: End grain
Reply #3 - Aug 28th, 2017 at 7:48pm
 
My last bowl was finished with wipe on poly. After several coats, every part had a nice shine except the end grain.That looked like it was never touched.
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Ed Weber
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Re: End grain
Reply #4 - Aug 28th, 2017 at 8:57pm
 
End grain absorbs or draws in more finish the the side grain due to it's physical construction. It's not uncommon for end-grain to require several more coats of finish than the side-grain to achieve a uniform sheen.
Many people use a sealer of some type so that the finish builds more uniformly
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Lee Watermann
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Re: End grain
Reply #5 - Aug 28th, 2017 at 9:17pm
 
When I turn end grain spindle work, Like mill knobs, I find the grain often will not take finish as it seems to separate it. Especially walnut and often cherry. I think an oil in the end grain is doing it. I started sealing the end grain with thin CA  before the finish and now no issues. The end grain comes up to gloss like the rest of the mill.
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Bruce Kamp
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Re: End grain
Reply #6 - Aug 29th, 2017 at 5:27pm
 
When I turn bottle stoppers I run into the same problem with end grain. I usually coat the stoppers with thin CA and then polish. The end grain is usually a lot tougher to bring to the shine of the rest of the stopper. Recently I discovered that if I use medium CA on the end grain, then sand with 240/320/400/600 I get a decent shine. My latest "break through" was when I then used my Bealle Buffing system to do the final polish. That is when I was able to get the entire stopper to shine the same.
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Mike Nathal
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Re: End grain
Reply #7 - Aug 30th, 2017 at 7:06am
 
From my experience, I don't think the end grain is "not taking finish."   I believe the opposite is true, like Ed posted.  The end grain is absorbing the finish and requires more coats.  You can see this by putting a few drops of finish onto the end grain and watch it disappear into the wood.   The CA glue is acting like a sealer so that the finish is not absorbed as much and builds a film quicker.
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Ed Weber
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Re: End grain
Reply #8 - Aug 30th, 2017 at 7:59am
 
Mike Nathal wrote on Aug 30th, 2017 at 7:06am:
The end grain is absorbing the finish and requires more coats.


+1

Thanks Mike
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Don Stephan
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Re: End grain
Reply #9 - Aug 31st, 2017 at 11:08am
 
A gloss shine requires a glass smooth surface, so that every photon of light is reflected perfectly parallel with every other one. An open pore wood will not develop a good gloss until the surface is perfectly smooth. Finishers have in the past converted a open pore wood to a perfectly smooth surface by spraying several coats of sealer (which is relatively easy to sand) and then sanding back the built up film until the surface is perfectly smooth. This results when the built up film on the solid areas of wood is sanded back to be flush with the unsanded built up film in the open pores, so the surface is now glass smooth.

Apply a uniformly thick layer of film building finish (sealer, varnish, et cetera) on a bowl. That layer sits on top of closed side grain, but has descended somewhat into the "holes" in end grain. Successive coats of finish build on that first layer continuing to build a uniformly thick film, but not a perfectly flat film, because that first dried layer was not perfectly flat.

If brushing or rubbing on the layers, it is possible on each application to trap a bit more of the finish in the lower areas, and gradually build a thicker film on them, but at the same time a thicker film is being built on the initially closed, smooth surfaces, and thicker film overall film is not always attractive or functional (it is more prone to chipping).

To experiment, sand well a piece of ash or oak board and spray a couple wet coats of shellac on it (a can is relatively inexpensive, shellac dries relatively quickly, and is easy to sand when fully dried), and let dry overnight.  The following day, a raking light should show a relatively shiny surface on areas of late season growth (smooth wood) but depressions on the open pores (early season growth).  Spray a couple more wet coats.  The third day, sand back with 320 grit the finish on half the sprayed surface.  After 10 seconds of light sanding, wipe clean and the areas of late season growth will show a uniformly dull surface but the open pores probably will be shiny spots because their surfaces are lower and the sand paper did not reach them.  Spray a couple more wet coats over the entire board and let dry overnight.  The following day, continue light sanding over that half of the board until all the shiny spots disappear - the surface of that half of the board is now perfectly flat.  It is quite possible that the other half of the board still does not show a perfect uniform sheen because the open pores there are not filled flush with the surrounding late season growth.  Spray one more coat over the entire board and let dry overnight, then compare the sheen on the two halves the next day - the half that was sanded back likely will show a uniform sheen while the other half that was not sanded back will not.  Compare also the thickness of the built up film on the two halves of the board.
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« Last Edit: Aug 31st, 2017 at 11:21am by Don Stephan »  
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