Raised Grain from rain

[dickhob]

I just finished a 2x turned cherry bowl and power sanded it to 400 grit. I raised the grain with alcohol after 150. I was able to get out almost all of the tearout- certainly good enough for a salad bowl.

It turned out very nice and really felt smooth. My shop is in my garage. It was raining when I went back to the house and a few drops hit the bowl. The raindrops raised the grain again- much more than I would have expected.

I let it sit for 30min or so and sanded the rainspots with 600 grit. Felt smooth, but I could still see the raindrops. I put a coat of tung oil on. I figured the drops would blend into the surface after the tung oil- I was wrong.

I've wiped the surface several times and will let it dry until I can't feel any oil, but those spots are still going to be there. I'm hoping a good rub out with 0000 wool or scotchbrite will get me to a consistent surface for another application of oil.

Am I on the right track? Tung oil is new for me so I'm not sure the best approach to fix this.
Thanks
Dick

 

[Ian Thorn]

If you get water spots on unsealed wood you need to wipe it allover with a damp cloth using clean water,now you have resealed it you may need to resand and finish

 

[Rob Wallace]

If you are raising the grain as part of your sanding routine, why did you choose alcohol? Water is far more effective to do this; you obviously can now see that fact. I would drop down a grit rating or two (...perhaps re-sand at 100 or 120?)to open-up the surface from any applied finish, wet the entire piece with water, allow to dry thoroughly, and then take your sanding through the abrasive series again. If doing this on the lathe, sanding in both forward and reverse might speed-up the process to achieve good "cut" on the raised fibers, although some might argue with this as being actually effective.

Tung oil is no different from any other applied oil finish. You are probably experiencing significant differences in surface treatment following the water event that results in different levels of porosity into which you are asking the wood to absorb the oil uniformly. If you have burnished the surface by going to 400, and the other areas have been treated differently due to the water, it is likely you will see those differences in the surface due to differential absorption of the oil finish. I would take the whole piece back to 100 or 120 grit to start, then and apply oil after 320. You can also wet sand with oil to generate that silky smooth finish, done at the higher grits like 320 or 400.

Good luck with completing your piece!

Rob

 

[Thomas Stegall]

Rob is correct, water does tend to raise the grain more than alcohol. Alcohol evaporates faster so you can get back to sanding sooner and produces a more uniform grain raising response than water. Some species have very little response to water (some dense, resinous species) so it doesn't always provide an advantage over alcohol, plus if the work is still on the lathe alcohol won't promote rust on the lathe. These are a few reasons why some people prefer alcohol including myself.

However, your problem is two fold. 1) You need to use alcohol between 320 and 400 due to the level of surface removal of 400 and the grain raising effect of alcohol. Following alcohol with 600 will not sufficently cut the grain raising effect, and will do very little following water. 2) Since you have water contact on only some parts of the wood rather than uniform grain raising you need to sand beyond the grain raising effect to establish a uniform surface and then proceed with grain raising and finish sanding. With most domestic species (including your cherry bowl), you will need to go back to about 220-280 get it the surface uniform and then use water between 220-320. With more dense or slower growing cherry you might be able to use water between 320-400. Or use alcohol between 320-400. Good luck.

 

[MichaelMouse]

Alcohol is NOT highly polar, therefore it does not bind well (remember the term "bound water?") to the cellulose. Water binds and swells the fibers. Why wood shrinks when it dries, yes? So use water, and be fairly generous when setting the fiber. Damp isn't really going far enough, soaking is more than you need. One of the OTHER reasons why alcohol "drying" violates the rules. Hydrogen bonding favors the more polar part of the mix.

If you have compressed air, it'll dry the surface fast, so no worries.

Sanding to 400 doesn't mean the same thing with the European system as it does with imperial mesh. P 400 is about the same as 320 per inch mesh CAMI. It also means something different when you're rotary sanding than when you're sanding up grain or down grain. Personally, I set after a rotary P400, then sand with P400 along the grain. Final set, and sand up grain only. Seems to make a reasonable surface.

Steel wool is another great option for close-grain woods. Works like mini-scrapers, with the sharp edge of the steel cutting the wood. Not good for open pore stuff. Even a blast of air won't clear well enough.

Oh yes, since oil (non-polar) doesn't H bond to the cellulose much, any water that works its way through unblocked pores will wick into a mess. Ask the guy who believed the bunk about mineral oil and beeswax "finishes", only to learn the drawbacks when it misted rain into his tent at a show. :mad: All kinds of white spots. Try warming the whole thing with a hair dryer to get the moisture out, sand and re-coat.

 

[Thomas Stegall]

White spots on a tent full of inventory? Wow, that must have involved a lot of time reworking items? Ouch. I recently tried using Tung Oil and beeswax as an experiment. I wasn't impressed with the results. Raffan seems to like beeswax and recommends using furniture polish regularly to build up a patina. But the polish my wife used apparently had too many solvents and instantly ruined the finish.

 

[dickhob]

OK, this has been great so far. I really appreciate the responses.

I used alcohol instead of water because I wanted the fast drying effect. I'm kind of impatient when I'm getting towards the end of something like this and waiting for water to dry drives me crazy.

I didn't know to really wet the piece. I've always just got it a little beyond damp.
Can I use a heat gun to speed up the drying?

I assume because I've already got a coat of oil on, water is not going to be of much help now.


The piece is off the lathe so I'm going to have to hand sand.

Here's my plan please correct if I'm too far off.

I'll give the bowl another day to dry. It feels dry, but I can still feel some oil residue on my hands- its dry, but certainly not cured.
Then sand with 150, 220 to a uniform scratch pattern. Then 320and 400.
Then refinish with oil.

I've never tried using oil during sanding. 320 or 400?
If I use the oil, do I put a finish coat immediately or wait a day or two for drying?

I'm not looking forward to all this, but a tent full of inventory???- enough to make you give up turning-- almost.

thanks
Dick

 

[Owen Lowe]

Can I use a heat gun to speed up the drying?

I use an old hairdryer when I grain-raise. Be very careful with the heat gun - they get wayyy too hot for this need and you don't want to crack (or singe) the wood. Also, when you shut off a hairdryer it won't melt or scorch anything the end touches like a heat gun will.

You probably have an old hairdryer stashed somewhere in your house. At worst, you may have to hand over a buck at your local thrift store.

 

[Gretch Flo]

walnut oil/beeswax

Michael-will walnut oil/beeswax spot the same as mineral oil beeswax???? Gretch

 

[MichaelMouse]

Imagine it would if the oil were uncured. It's a matter of how long it goes unnoticed, too. Sort of like grain raising on an unfinished piece, you need a bit of time to swell the fiber. First it has to weasel its way in.

Fortunately I only had a dozen pieces with the oil/wax exposed. Most were conventionally finished.

 

[Jake Gevorgian]

I don't know if it's safe to use this method, but Naphta (not available in California) makes the oil dry very fast. That's what we used (just a tiny bit) with oil based wood stains (paint thinner and UTC color pigments.) Just so you know, Naphta doesn't smell decent.

 

[KellyDunn]

I use an old cotton sock kind of wrung out and get the work damp. If when finished and a gust of wind gets raindrops on a finished raw piece. I get the whole thing wet again. I have put finish over spots and they never went away. Big mistake. I have tried sanding back. But not as much as has been recomended. So it may work for you. I have a fan blowing on the work. Its raining today so it will take five minutes or so for the work to be dry. A hot sunny day and its less than a minute. The forward and reverse I do then with 320 grit handsanding creates plenty of heat in case some moisture stays. I do not get the work sopping wet. If I have a dent I keep putting water on the dent to get most of it to raise back out.