Problem with gaps in Red Oak

[Egraff]

Hello All,

Background:

I am building a project out of red oak, and I am very close to wrapping up this build. I've already pre-finished parts of the piece and am sanding the rest to fine grits to begin the final finishing.

A few weeks ago, I noticed that the lid / top piece for this project had warped badly, for some unknown reason. I've done far too much work on this lid to replace it, so I did my best to fix it. I very lightly dampened the surface with water and then pressed it under light weight / pressure for a week to return it to its flat shape. This actually worked quite well... the piece is almost good as new, and has retained its flat shape for 2 weeks.

Now, the problem:

As I have begun sanding the "fixed" lid / top piece, I have noticed small gaps appearing in the wood surface. They are anywhere from just a few mm to 3/4" long, and are roughly no larger than 1mm wide. These gaps all seem to be appearing in 2 places only: first, along glue joints of the panel (it was a glue up from 8 smaller strips), and second, in/on short dark lines that I thought were part of the wood grain, but am now not so sure??

The problem is, every time I fill these gaps and then start sanding the lid again, more gaps seem to open up. I just don't understand what's going on here........

I have attached a super close up picture of these dark lines that turn into gaps... as I mentioned, I initially thought they were just part of the wood grain. The photo is just of the lines, but for the gaps, just imagine that some of the dark lines vanish and are replaced by gaps in the exact same place (if that makes sense).

Solution:

Does anyone know what is going on here / what I can do to fix this? I'm getting to the point where it seems pointless to keep trying to fill these. I'm thinking that maybe the finish will at least fill them somewhat once I start to apply it? (b/c I need to move forward with my sanding, and every time I fill a gap I have to go back to a rough grit again...)

Thank you for your input!!!

Best,

EG

[Bombarde16]

Looks like those are the actual ray flecks. I can't imagine that these would open up more than the pores in the growth rings, though. Red oak is known for having large pores and I wouldn't worry too much about it.

What's your finish of choice? I'd go ahead with it and, if it still bothers you, build your next project out of maple.

[Dan S]

I'm with rob, that looks like normal rift or quarter sawn Red Oak grain to me. also to add to Rob's question what grits are you sanding with, and how are you sanding, by hand, ROS, palm sander?

[Egraff]

Rob and Dan,

Thank you for your quick responses - I appreciate it! And I know... to me it seems like the lines are the normal grain too - this is why I'm confused. I'll try to photograph one of the "gaps" that opens up and post it to this thread, however I'll have to see if more open (hope they won't!!!) because I filled all that remained last night.

I'm using Arm-r-seal satin for this project. As I mentioned in the original post, I've already prefinished some of the panels in this project using this product, and I am very pleased with how they look with the arm-r-seal.

As far as grits are concerned, the problem with gaps opening up keeps happening when I sand with 100 grit using mainly ROS and occasionally quarter sheet palm sander in tighter spots. I keep being ready to move to finer grits, find more gaps that have opened up, fill them, re-sand with 100, then find more new gaps, repeat....

For the prefinished panels I went from 100 120 150 180 220 with the ROS and as I said, am very pleased with how they look.

Is anything I'm doing here in the sanding / finishing process jumping out as a mistake? Thanks!

[Dan S]

I'm using Arm-r-seal satin for this project. As I mentioned in the original post, I've already prefinished some of the panels in this project using this product, and I am very pleased with how they look with the arm-r-seal.

As far as grits are concerned, the problem with gaps opening up keeps happening when I sand with 100 grit using mainly ROS and occasionally quarter sheet palm sander in tighter spots. I keep being ready to move to finer grits, find more gaps that have opened up, fill them, re-sand with 100, then find more new gaps, repeat....

For the prefinished panels I went from 100 120 150 180 220 with the ROS and as I said, am very pleased with how they look.

Is anything I'm doing here in the sanding / finishing process jumping out as a mistake? Thanks!

I'm almost sure your issue is that you have some boards that have course grain, and you are sanding through with 100 grit. if i sand between coats of a finish I always do it by hand and use one grit 220 or 240 depending on what I have on hand.

Are you trying to fill the grain with the finish?

[Egraff]

Sorry Dan, I don't think I was clear enough in my previous post.

The problem with the gaps is not occurring on my prefinished panels... those look great. In between coats of the prefinish I sanded by hand with fine paper.

The gaps instead keep appearing on my lid/top piece (from a different original board of wood) that I have not applied any finish to yet.... I'm only now taking it through the sanding process, and am currently stuck on 100 grit b/c every time I sand at 100, fill the gaps, and re-sand at 100 to clean up the fix, more gaps open up.

NEW THEORY:

I think that the wood I'm using for the top / lid is defective in that it has many tiny gaps or splits in various places inside of it that somehow correspond to dark lines in the wood grain. When one of these gaps / air pockets / splits / or whatever you want to call them gets sanded through, it exposes itself to the surface and appears as a "gap" in the wood.

So, once I fill these gaps and re-sand the wood, I expose more splits in the wood and hence the new "gaps".

I am attaching a picture of one of the gaps to this message - if you look closely, you can see the dark brown outline of the dark grain line from where this gap appeared.

Does this make any sense? I just can't think of what else could possibly be going on. Hopefully this won't affect the stability / longevity of the piece!

Thanks,

EG

[Dan S]

at that magnification, that looks like a small dried out pitch pocket.

here is a good shot of a pitch pocket in Douglas Fir.

http://4.bp.blogspot.com/-rVHm_bxm3Vk/T4xDyK2rzcI/AAAAAAAACUE/uy9DYgRn-XQ/s1600/DSC_0012smltLOWES+HomeCtr+Doug+Fir.jpg

[TRBaker]

If I had to guess, you set into motion a checking problem when you wet the lumber and then put it under pressure to counter the warp. You may be dealing with a piece that is case hardened and is now trying to stabilize itself after the addition of the moisture. I may be totally wrong, but it seems like you have done everything within reason to fix what would normally appear in red oak.

[Dlhunter]

What are you filling these gaps with?

Are you unhappy with the color of the gaps or just the fact that there are gaps?

[Egraff]

Thank you all for your continued responses.

Dan, yes! That pitch pocket looks exactly like what is appearing in my red oak. This supports my hypothesis that there are small gaps (or pitch pockets) throughout the wood that I keep revealing with my sanding. I just had no idea that pitch pockets would be in red oak and be so absolutely tiny!!!

Troy, you might be right, although for my project's sake I hope you are wrong! <smile>

Through a lot of reading I found that the wet / weight method seemed reasonable given the amount of warping in my board (it was too cold out to try the sun/grass/water trick. But yes, case hardening is certainly a possibility to keep in mind.

Darrel, I am filling these gaps with a blend of sawdust and glue. I initially tried using some wood putty, but have found the sawdust mix to be a much better color match for this specific piece of wood.

And I am unhappy with the fact that every time I fix all the gaps and am ready to move on with my project, more gaps appear out of nowhere!!! <smile> This lid is the main focal part of the piece, so I certainly don't want gaps / cracks appearing in it. Hence the problem...

Again, everyone, thank you for your continued insights!

[Bombarde16]

OK, at that magnification, it's definitely a ray fleck, not a pitch pocket. Hardwoods aren't going to give you the gummy, resinous goop that you get out of construction lumber. (That's why you can smoke meats with them, after all.) Remember, the medullary rays radiate from the center outwards. In a flatsawn board such as you have there, that means that they're perpendicular to the face. Larger rays can certainly open up like this. Perhaps in another life that board would have revealed a beautiful figure if quartersawn...but we'll never know that now.

Is anything I'm doing here in the sanding / finishing process jumping out as a mistake?

No. If there's any mistake to be named, it's way back in the selection of red oak for the project. If this sort of texture bothers you, choose a different wood. Maple is glorious for furniture and its grain is nearly non-existent..whence its popularity among some futurist designers. Poplar and aspen are likewise almost texture free. Any conifers would also serve you well.

As for the project you're working on now, I suggest you take a deep breath and leave the gappy rays alone. Finish the project, take it as an object lesson and move on with a smile.

[Eric.]

I don't know, Rob. I don't really see ray fleck there (not ON the split anyway). Looks more like case hardening to me, like Troy said. Did you see the post Barry put up a few days ago about the QSWO he got? ---> It's a much more extreme example, but it seems more likely to me. That wood is pulling itself apart for some reason.