The picture below is a close up of a bookcase that I am finishing made with Red Oak. Small dark spots showed up after I stained the wood. Does anybody know what they are, and how to keep them from happening again? I sanded to 220grit. I suspect that the wood was not sanded properly??
Replies
Sorry, I can't help with the spots, but I do want to offer you the highest possible praise for posting a picture that is intelligently composed, sharply focused, brightly lit, and large enough to show the relevant detail. Those four attributes combine to push your photo well into the top 1% of pictures I've seen posted on the internet. Very rare. Congratulations.
Edited 3/9/2004 2:41:42 AM ET by Uncle Dunc
It is a great pic.
I'm not sure what caused the spots. They look like the same type of staining that iron and water will cause in oak. and they are around the pores. I could imagine that the tree itself might have lived in an iron rich soil and by pulling water and such through the pores stained them black. Did you use a water based finish? It could also be something like steel wool bits trapped in the pores and staining them black with the moisture content in the wood.
Just my guesses.
Justus Koshiol
Running Pug Construction
The wood has 1 coat of stain, 1 coat of sanding sealer and 1 coat of varnish. All oil based. The spots appeared after the 1st coat of stain. I think I'll try several defferent test pieces with different wood, sanding, and stain.
Also consider sealing the wood with shellac then using a dye stain; then a topcoat.
Regards,
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934
Boris,
I have considered a shellac finish, but have not tried it yet. Is it possible to use a grain filler to smmoth out the wood pores? If so when is the grain filler put on? I also wonder if shellac is as durable a finish as varnish.
Thanks for the praise. Looks like I'm better at taking pictures than finishing oak.
Unisaw, I'll certainly second earlier praise of you skill with a camera. It's an excellent photo.
As for the dark spots, I'm curious as to how dark of a stain you used. The reason I raise this point is that the photo indicates dark pigment in the earlywood vessel lumens that is approximately the same hue as the finer spots. The answer to your puzzle might simply be that the smaller dark spots are the result of the same stain being trapped in the lumens of the smaller latewood pores.
See if you can examine one of these smaller dark spots that happens to be right at the end of the board (or cut a scrap of the board at one of these spots and look at it under 10X magnification) to see if the perpendicular cross section of the same spot indicates that it is a pore (vessel).
Jon,
Thanks for the information. The oil stain is "Fruitwood". I consider it a medium to dark color stain. I will cut a piece of the board and look at it from the end, I'll let you know what I find.
I am looking for a better way to finish red oak. I currently use a sanding sealer and several coats of brushed on varnish. This finish is acceptable but not great.
This is for a bookcase so I would consider it will get alot of wear. I also like the idea of a grain filler to get a smoother finish. What is the best process to stain, seal, and topcoat the wood for a bookcase?
I have two questions, what sort of camera are you using as that is a great picture.
Second, how did you get it to show up as an image rather than a link?
The picture was taken with a Nikon D100 with a macro (or micro) lens. I use a tripod, flash strobes and manual camera settings. Lots of light with a small f-stop (like f16) and a solid tripod works wonders for any camera. If I get time I'll post a picture of the setup.
I process the pictures in Photoshop, correct color, resize, and use unsharp mask. I shrink the photos down to 100kb to 150kb. (from 2,500kb) We could get more detail but with some of the modems still at 56K, it can take forever to view.
After processing, I post the picture on a web site (like pbase etc.). I pull up the photo and right click and then copy the photo. After the photo is copied, I paste it into the "knots" message area.
Anyway, Here is the bookcase so far. It has a finished roof, 3 5/8" crown molding an 3 1/2" base. The missing center section will be installed when the final installation in the room is done. It is 8' high x 8' wide x 12" deep so I have to keep it in pieces to get into the house.
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Unisaw, red oak is a ring-porous wood, which not only means you need to use a filler in order to get a smooth surface...it also means it is more difficult to get a uniform color when using dark stains. The pigment tends to lodge in the earlywood pores, but wipes off the denser latewood tissue, giving the figure excessive contrast.
The use of a filler solves the smooth surface problem and there are a couple of ways to go about getting a dark but moderately uniform color. You can try using a dye instead of a pigmented oil stain or, if you are going to fill the wood anyway, you can use a varnish stain (meaning a varnish with pigment in it, so that the color remains in the film of the finish).
Dye doesn't tend to build up in the earlywood pores quite as much as does a pigmented oil stain, so you don't get as much contrast, but you'll want to experiment on scraps until you're sure of what you'll get...because it can be very unforgiving. To simply apply a clear sealer coat and then use a pigmented oil stain works on some woods, like pine, but it won't help much on a wood as ring-porous as red oak, because the pores will remain open enough to still trap the pigments in the stain. If you first fill the pores with a stainable filler, you can overcome this problem...but the easy way out is to use a varnish stain as a final step in the finishing process, so that you have complete contol of how much color you introduce ONTO the surface.
Even varnish stain will tend to collect in the pores, if you don't at least give the surface several coats of a heavy bodied, clear varnish first...but on a filled surface you can achieve virtually any color you want. The downside to varnish stain is that too many coats of it will begin to mask the wood's figure. However, with a bold figured wood like red oak, you'd have to be pretty heavy handed to completely bury it.
Hope this helps... and be sure to report back on what you discover regarding the mystery dark spots. You've got me curious.
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Jon,
I think you are right. If I have the smaller latewood pores marked correctly, it is exactly where the small spots are showing up. I assume the larger earlywood pores are visible as grooves in the wood. In any case both pores are taking the stain the same way/color.
The left side is from the same piece of oak. The left side is unfinished, the right side is stained.
So to get rid of the spots, I am thinking that the first step would be a coat of grain/pore filler to fill the smaller latewood pores, then apply the stain or wood dye. I have not tried wood dye yet, but that will be the next step.
Anyway, thanks to all for the help.
Yes, you have the wood's anatomy correctly labeled...so, it looks like you have the mystery solved.
It also sounds like you're experimenting with the right solutions to avoid these dark spots in the pores. The filler will probably prevent them in both the earlywood and latewood pores. And since you want a smooth surface anyway, that would seem to be the way to go. Dye will give you a more uniform color, but once you have all the poors filled, even a pigmented stain won't produce as much contrast as it did on the raw wood. Good luck.
Jon, what filler do you recommend for oak that is to be stained?"Everything should be made as simple as possible, but no simpler." A. Einstein
http://www.albionworks.net
I've been using Rockler's Wunderfil, but I don't have any strong brand loyalty. The key is to use a stainable filler and experiment with tinting it and top coating it...even if the filler's base color looks close. Because of differences in the porosity of the filler and the wood tissue the color often shifts when the subsequent top coat is applied.
Unless I'm using one of my standard finishing methods on a species I've worked with many times, I always take the finishing process through all the steps on scraps before I begin applying it to the completed project. And you definitely want to do this when using a filler on an extremely porous wood like red oak. Once it's in there, it's in there and you'd have to remove about a 1/16" of the surface to get back to a raw wood starting point...So, make sure you do it just once and do it right.
I've never used the one from Rockler, Jon, but my filler of choice is plain old plaster of paris. It's patchable, tintable, stainable, redo-able and it is cheap.
Lee
Lee, it wouldn't surprise me if plaster of paris was the primary ingredient in all of these commercial fillers. I haven't used the pure stuff on the supposition that it might be a little brittle or powdery under the top coat...but I'm certainly not a finishing expert. I have my own trusted methods, the product of having made just about every mistake possible at one time or another, and I don't wander off into new techniques or new products much.
Do you add anything to the plaster of paris as a binder?
Edited 3/13/2004 6:32 pm ET by Jon Arno
Nope, no binder. I just mix it into a thick paste and apply it just as any other...with a ton of elbow grease. I used a Benjamin Moore filler on a table recently and nearly lost the top...the filler would not stick to itself so there were no redo options. There were about 35 inlays and a few needed a bit of futzing, well the futzing led to the top needing more filler in some areas, the B. Moore would not stick to itself so those areas took the stain differently, which led to days of futzing getting the color right. The B. Moore is a solvent based. I swore I'd never use that stuff again, or any product like it. Plaster of Paris will stick to itself so I'm sticking to it. It's rare I use filler, in fact, the only time I use it is to knock the chatoyance way down. I might even skip the filler for that in the future and just tint my varnish.
Lee
"Fruitwood" stain has both dye and pigment. Umber is the pigment and that's what's lodged in your pores. To avoid this look use stain with only dyes. Oak however, is one wood that looks good with clogged pores. The umber pigment will appear to lighten as topcoats are applied but it will always accent the springwood.
Lee
Oaks have large pores. If you used a pigment type stain, the pigment gets deep into the pores and stays there. Wiping does not get into the pores so the pigment stays there.
Dye type stains are better to use on large pored wood if you don't want the pigment to show in the pores.
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