Replies

1. 
   RMillard | Dec 12, 2003 06:15pm | #1

   GJ13

   Actually all three. For varnish ,polyurethane and I would guess lacquer (I don’t use much lacquer) soapy water makes a great rubbing lubricant. The addition of soap breaks down the surface tension of the water, but has the disadvantage of contaminating the surface, requiring you to thoroughly sand with mineral spirits or naphtha, if you find you need another coat. For shellac with its limited water resistance, I use mineral spirits or combination of mineral spirits and mineral oil. Here again the addition of oil contaminates the surface, although shellac has an amazing ability to seal in almost any contamination, I’d still carefully remove all traces of oil, if a re-coat were necessary. Some people also wet sand oil finishes on bare wood, which results in a slurry that will fill the grain. I have not done this, because I don’t consider oil a finish, although it is a vital component of finishing.

                                                     Rob Millard

2. 
   HowardAcheson | Dec 12, 2003 06:41pm | #2

   The first consideration is the finish. You wouldn't want to use water on a shellac or waterborne finish but, water is an excellent lubricant for wet sanding. The intent of the lubricant is to float the residual solids (dust) away rather than have it dull the grit of the sanding medium. In other words, it keeps the grit clean and cutting fast. Any liquid can work as long as it isn't a solvent for the finish.

   For oil based and lacquer, water, mineral spirits, or mineral oil will all work.

   For shellac, mineral spirits or mineral oil would work.

   For waterborne, use mineral spirits or mineral oil.

   As always, be sure the finish is fully cured. For oil based finishes, this can be 3-4 weeks.

1. 
   gpasewicz | Dec 12, 2003 07:05pm | #3

   Thank you.  After I sent the question I suspected it might be determined by each situation.

3. 
   Tao | Dec 13, 2003 03:06am | #4

   I have done an awful lot of cutting and rubbing on all kinds of finishes, and whenever I can, I use water with just a few drops of clear dish soap in a pint of water.  Water alows a given grit to cut faster than anything else.  Water is fine, for shellac, too.  It's alcohol that shellac doesn't like.  A while ago, I put some water on a piece I had just finished in shellac, put a jar over it upside down to keep it from evaporating, and two days later when I wiped the water off, there was not a mark.  I've never taken any pains to do more cleanup than wiping all the residue off, either, before recoating.

   Mineral spirits cuts slower than water, and can be used where water is not suitable, such as on waterborne finishes.  Seems to take 5 to 10 times as long as water to evaporate.  VM&P naphtha cuts fast & evaporates quick, otherwise works like mineral spirits.

   You can also use a vegetable soap like Wool-lube.  It works especially well with steel wool.  Pretty slow for sanding, unless you cut it a lot with water.

   I seldom use mineral oil on a finish.  Water and mineral spirits evaporate completely.  Oil doesn't; not in any reasonable amount of time, at least.  I do use paraffin oil, a form of mineral oil, when rubbing with pumice, but there are too many easier ways available these days.  I also use a few drops of paraffin oil when French polishing, but that's about it.

   Michael R.

   
   

   ---

   Edited 12/12/2003 7:07:18 PM ET by Woodwiz

4. 
   UncleDunc | Dec 13, 2003 10:09am | #5

   Or wet sanding could be when you're just starting the finish. Sanding the wood with a generous quantity of oil (or varnish, etc.) to make a slurry of oil and wood dust that gets worked into the pores. Gives the pores a very close color match to the rest of the wood.

5. 
   VeniciaL | Dec 13, 2003 08:57pm | #6

   BG and GJ13,

   That Word doc is one of the best descriptions of applying an oil finish I've read. Someone who has never applied one or who has had poor results should read it several times. It's applicable to any brand or home brew of the stuff. The key concept of those instructions is that while it's a foolproof method (no special talent is needed to brush or spray) it is NOT a quick and easy method if you want to achieve the beauty that a hand-rubbed finish can give. Another subtle point in the instructions, is that the author is using a product that contains not only an oil, but a varnish. It's an oil-varnish mixture and it's really the varnish that gives the wood its polished look. The oil (tung or linseed) brings out color and grain. It is possible to get the same polish without color development if that's desired by using a rubbing varnish, which is really just any varnish you chose, diluted with about an equal amount of solvent (add some wax to the mixture if you like, these formulas tend to get highly personal, but all work about the same.)

   I highly agree with his wet sanding recommendations, but I'd like to add two changes to the process. When I apply this kind of finish I do NOT want the pores to be filled. Pore filling is something you do, and MUST do to prepare a surface for a thick film finish (brushed varnish, for instance). I want the pores to stay open because it's the contrast between the pores and the polished plateaus of the wood between the pores that gives this finish a great deal of its charm. I select this finish for tropical hardwoods for just this reason.

   I do not start wet sanding until after I've applied at least two coats of the finish. Each coat having cured for at least 2 days. The wet sanding then begins to polish the top of the very thin finish film (it is VERY thin and delicate at this point - but won't be cut through because the fresh finish lubricates the 600 grit paper or steel wool). No wood slurry is produced and the pores fill little at all, if any.

   Different woods require varying amounts of this wet sanding- finish application steps, even though the wood surface is not being touched any longer. It's a matter of watching for the point of diminishing returns.

   My final application is something that's a little hard to describe. It's a technique that becomes apparent as you do it. It probably comes from having applied french polishing so often. The last coat is applied with a balled up piece of cotton barely wet with the mixture. I apply it with a french polishing motion, starting the pad moving before touching the wood and lifting the pad without stopping on the wood. One direction only - never back and forth. It leaves a gleaming, wet look that does not dull at all as the finish hardens. This last pass is a VERY thin top layer on the built up thin film on the wood. It's much easier than real french polishing. The oil/varnish finish is much more lubricating and slippery than shellac and the pad doesn't have a tendancy to "grab" if you get careless as can happen with real french polishing. It just takes a few minutes to experimentally find the right wetness of the pad to make this happen. Too little and there's no film laydown. Too much and there's enough finish on the surface so that it needs to be wiped down. Just enough and the film needs no further rubbing. it's as thin as it gets, right away. I've found that it's very hard to make this work well with finish that's been prepared more than a few weeks. It must be fresh. Something changes in the chemistry when it's been exposed to the atmosphere for more than that.

   VL

1. 
   BG | Dec 14, 2003 12:57am | #7

   Venicia L,

   Thanks for the information.  I'm about to rub out my brushed on lacquer finish...Deft.  There was an article in FWW that spoke about using a rubber made of dungaree material...similar roughness to the grass skirts you like to wear down there on the island, only you can't see through dungaree...and use a pullover product (not sure what that is).  I have not been able to find the pullover...and don't want to order on line. 

   The finish came out quite smooth.  I'll probably start with 600 grit and murphy soap and see how that hurts things...