Knocking back grain & danish oil without going white

[dilby]

Hi all -

I'm new to this forum and new to woodworking, which will probably evidence itself in this post, but I was really hoping someone could help me!

I found some oak floorboards stacked up in my loft, so I used them to make a new tabletop, and upcycled our old table (keeping just the frame and legs). I made it by glueing the boards first length ways in strips, then edge to edge to form a flat mosaic of the boards, then cut to length and sanded smooth. I finished with danish oil, and it looked good and I was happy. But about a week later, lighter patches started appearing which were rough to the touch. After doing some research online I discovered about 'knocking the grain back' which seems to be a necessary step that I didn't do.

So I got some 400 grit sandpaper and gently wiped back one of these areas by hand, which made it smooth again but unfortunately it's all turned white, and white dust has now got trapped in the grain, so it actually looks worse Is there a way to fix this, or am I going to have to resand the entire table back to bare wood, and then re-oil it all?

Many thanks

 

[marcros]

I doubt that this is raising the grain. The oil has probably sank into the grain, partially filling it. You have now "denibed" the oil finish and the dust has gone into the pores that are not completely filled. A wipe down with a tack cloth will remove the white.

Knocking the grain back is something that you do before applying a water based finish, to stop that water in the finish swelling the grain.

 

[dilby]

Interesting, thankyou. I will try simply whiping it down now although i don't like my chances getting a cloth into such small pores! What then would be cuasing the grain to raise like that after I oiled it? It was super smooth before I oiled it, and now it's smooth again after just a quick rub down.

 

[marcros]

I think that it is the finish sinking, rather than the grain raising. you have now filled it with sanding dust. you could wet sand with the oil and fill it that way- when more oil hits it, it won't show as white.

wait for a couple of other opinions and see what they say- there are people with a far greater knowledge than me on here

 

[dilby]

Just reading about wet oil sanding now - very interesting. I have some wet and dry here so happy to give it a go, but may wait as you say to see some other opinions - I'm not in a super rush and would rather get it right.

 

[marcros]

do you have any leftover timber? even with the best advice, it is always best to try it out first before going to your final project

 

[dilby]

Only tiny scraps actually - was lucky to JUST have enough. Could in theory test it out on a scrap but wouldn't give a great indication. But yes, it's a good lesson for the future to do that next time.

 

[dilby]

Okay a bit of an update - I lightly sanded the entire table until it was super smooth and then wiped it down with a wet sponge. Not white anymore, but now the entire table is rough!

 

[memzey]

You have raised the grain which is causing the roughness as described by Marcos above. You should either dry sand it followed by a wipe down with a tack cloth/vacuum clean/pressurised air blast to clear away the dust or wet sand it with oil (if you want to fill the pores).

 

[rafezetter]

I find wiping down with white spirit better than water as it doesn't raise grain, not even on pine (far as I can tell) and will flash off soon enough that you can continue with what you were doing.

If the grain was raised after that wet sponge it's because the sanding has cut through the oil layer back to the wood itself - so I'd suggest the wet sand with oil and wipe it off with a lint free cloth - cotton is best - don't take it all off as that defeats the purpose, just until it feels tacky.

Wipe off PERPENDICULAR to the grain so you don't drag out the oil + sawdust pore filler.

leave that to dry for several days at least and then sand again (de-nib) with 1200 grit on a block using no pressure - simply let the block sit on the wood and sand following the grain.

Wipe down again with white spirit and enjoy or repeat if there are pores still showing and you want it flawless.

 

[Phil Pascoe]

................. and don't even think about doing it with steel wool.

 

[custard]

I found some oak floorboards stacked up in my loft

Do you know that they're Oak, or do you think that they're Oak?

 

[thick_mike]

If you want a smooth finish with no pores, sanding sealer is probably a quicker way to go.

 

[CHJ]

Did the white patches look like a haze under the finish?
What was the temperature when you oiled it?
Are you sure it's not moisture in the wood you are trapping under the oil, had something warm like a coffee mug been placed in the areas that showed white?

Polymerising oil blends such as 'Danish oil' can take many days even weeks in cooler conditions to fully cure.
If sanded before fully cured then you risk breaking through the surface skin into un-polymerised oil.
How thick did you apply the oil, you aren't by any chance seeing surface texture changes as 'rough patches' due to oil skin wrinkling where applied too thickly. Are you wiping off surplus oil after a few minutes of applying so that there are no 'pooled' patches.