The Stovebolt Site Forums The Shop Area Making a Stovebolt Bed wood grain still showing low spots

help,
i've put on nine coats of minwax urethane(sanding in between coats w/320 grit 3m gold) and still have low spots in the wood grain. should i switch to 220 grit and keep piling it on? i sanded the wood first, and thought it was ready for the urethane. any and all replies are welcome. thanks,
-e-

Is it Oak??

Can you give us more info about the low spots and your work so far? I'm assuming these low spots are visible when you look down the length of the board at an angle? If the low spots are depressions that run across the short dimension, (at right angles to the edges of the board), they could be caused by the planer at the mill or by the drum sanders most mills use for production work. If that's the case, they never should have been shipped to you. Although we've seen a couple of recent posts about poorly finished boards from vendors, most vendors' boards don't require much sanding on your part...maybe once over with 150 grit, then once with 220, and a tack rag to get off the dust. Oak is a strong wood, but it's open-grained, and on new wood, you should use a grain filler. This is brushed on and wiped off and levels the grain for the finish coats. It won't fill in dips from sanding, though. In your case, if there are visible low spots that run parallel to the grain, i.e. along the long dimension, poor finish sanding may be the cause. Not being critical, but a lot of wood has been damaged by belt sanders left too long in one place, or by uneven pressure. Most bed boards from vendors require only an orbital sander or a vibrating sander to finish. Putting on more urethane will not fix the low spots. When you coat the board, you're adding the same amount to the entire surface, so the difference between the low spot and the rest of the surface remains constant. Using 320 grit is OK for light sanding between coats, but neither it nor 220 will take care of low spots now that you've got 9 coats of poly on the board. I know you don't want to hear this, but if you can still see dips in the surface, you may be looking at starting from scratch. The good news is that even 9 coats of poly isn't very thick, and a good chemical stripper with methylene chloride will get you back to bare wood pretty quick. Then use an orbital sander with 120 or 150 grit paper to get the surfaces completely smooth and level. Then sand with 220 before recoating. With polyurethane, you need to sand lightly between coats with the 320 grit to promote adhesion and you can put on as many coats as you want (although 3 should be enough).

yes it's oak. the low spots are in the grain itself. i was hoping to fill them all in like you do with build primer before painting. i don't see any spots that are because of the milling process. if i sand down the existing coatings, will the remainder stay in the lows? i didn't stain the wood, so if i cut through to bare wood, it should still be okay i think. maybe my assumption was that the urethane would fill in the grain. i hate to take it all the way back down, because it looks great. thanks for the replies.
-e-

Ed, Oak grain is very hard to get perfectly flat unless you fill the grain with wood filler. I use a product called Wood-Kote to fill open grain wood like Oak and Walnut. Yes you would have to take it down to bare wood again to fill it. You will not harm the wood by taking the urethane off. Since you didn't stain it that eliminates one possible problem. Can you post a closeup photo of your bed wood? It might be easier to take your boards to a woodworking shop and have them plane the urethane off. Some shops have large belt sanders also. You could get them to sand the boards for you. I have used this process to flatten out table tops that I have built. I have used my planer to take the urethane off my original pine boards. Some shops will not run urethane boards thru their planers because it will dull or chip the blades, which is an added expense to them. Unless you do not like the raised areas of the oak grain there is not much else you can do. If you feel that the boards look great as is, just leave them that way. that would be a natural oak finish. I have built many cabinets out of Oak and didn't fill the grain. It is more of a natural finish. If you have any more question that I can help you with please ask. Frank

Several years ago we sold finished bed wood boards as an option. Our standard finish was 3 coats of Helmsman Spar Urethane, sanded between coats. Occasionally we had a flaw as you describe, a narrow line right over a grain that just would not accept the finish. No matter how many coats of urethane was applied, it never would bridge across the line. The way we got rid of it was to block sand the board back down to wood and wash the area with solvent such as thinner or the solvent you would use before painting a car. Then wipe it dry and lightly sand again with 180 or 220 paper. Blow out the dust from all the grain areas. Be sure the air is filtered clean and dry, no oil or water in it. If the air has oil in it you will inject the oil right into the grain of the wood when you are trying to clean the grain. Tack wipe the boards and you are ready to spray it again.

It is frustrating, but whenever a finish doesn't adhere to a surface, there is something on the surface that is not compatible with the finish and it must be removed.

Mar-Ktech

once again,
thanks for the replies.
frank, i will send you an email with a pic. i like your idea about just leaving it alone.

mar-k, there are no areas on any plank that are not adhering. i don't think i could apply it any cleaner than i did this time. there should be no problem with me not using a wood sealer is there? i was going for the "bartop" look. i guess i'm just a bit too fussy!!!
-e-

Applying paste wood filler on any open grain wood, especially red oak, will eliminate the waviness over the surface of the board. Paste wood filler should be applied by a wide blade putty knife and worked into the open grain of the wood. This process is followed removing the excess and finish sanding with an orbital sander with 220 grit paper.

This is followed by application of a sanding sealer. The paste wood filler fills the open grains in the wood, due to machining and the sanding sealer neutralizes the "raising the grain" process, by securing the loose elements of the open grain cells of the wood. After drying, sand the wood with an orbital sander with 400 grit paper. Change the paper frequently, to avoid gumming up the paper.

When introducing the finish, that is high in moisture content, the grain does not raise, thus a flat surface, for applying the final finish coats. This is what I learned from working with finish guys at the furniture shop. Their table tops were smooth as glass, even in the right light.

I hope this information is helpful.

Tony

LOW SPOTS??? Thats factory..or you used a belt sander.Putting paste over oak..I would not do that either, with all respect to Tony...You can strip it..but if the low spots are factory ..then I would get out the palm sander, You can also put a coat of sanding sealer to start. This will lift the grain alot and it Might...Might help with the low spots. But you will need to sand it after it has dried with 220, its a lot more sanding then sanding after a coat of regular ureathan...It must be completely dried..a good way to tell is if it powders up while you are sanding. If it rolls and makes boogers while you are sanding it is not dry enough.Next...throw out the Minwax..and get some Helmsman ..or Marine urethane. Both of these products will give you a slight amber tint with 4 or more coats ..maybe less..3 or so. Minwax is good for interior wood work.If you switch to Helsman...I am not sure what will happen if you do not strip your wood...so be ware my friend..it may lift the minwax...and then the fun really begins.. So Strip, palm sand ..sanding sealer (1 coat)sand 220. tack, damppen a white cotton rag with thinners, wipe,then start the building process again. With helsmans..