Replies

1. 
   UncleDunc | Mar 05, 2004 10:02pm | #1

   The one time I tried linseed oil on cocobolo, it stayed sticky, too. I think shellac would be my next choice.

   PS - Sounds like a nice combination of woods. Got a picture?

   
   

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   Edited 3/5/2004 2:03:10 PM ET by Uncle Dunc

2. 
   Crunk | Mar 05, 2004 10:36pm | #2

   Your project cries for a simple wax finish.

1. 
   PlaneWood | Mar 05, 2004 11:40pm | #3

   Here's my suggestions, not necessarily in any order.

   1) wax

   2) soak in acetone for 10 minutes then poly.

   3) seal with 1# cut of dewaxed shellac, buff with 0000 steel wool, then lacquer.

   lacquer will fish-eye on Cocobolo if you don't use dewaxed shellac.  At your present stage, i'd wipe off the poly with a rag wet in paint thinner, let it dry, then do either 1), or 3).  Deft Clear Wood Finish (lacquer) in a spray can available at Walmart or HD will do fine.  4 or 5 coats then buff to desired appearance.

   PlaneWood by Mike_in_Katy (maker of fine sawdust!)PlaneWood

3. 
   OneofmanyBobs | Mar 06, 2004 12:30am | #4

   The oil in cocobolo definitely interferes with curing of most varnishes and polyurethane.  Same problem with teak and a few other oily woods.  I use a wash coat of dewaxed shellac.  Do not sand after the wash coat.  Also, a vinyl sealer for lacquer might work.  Depends on the brand.  Wash off all the poly with mineral spirits.  Let it dry a couple days.  Wipe on a coat or two of shellac and you can put any other finish on top. 

   The poly might eventually cure if you leave it in a hot sunny place for a while. 

1. 
   PlaneWood | Mar 06, 2004 06:03am | #5

   Just to illustrate how much oil and wax is in Cocobolo, do this:

   Use a dull 1/4" bit in a drill press set at medium speed and rapidly drill thru a block of  Cocobolo about 2" thick.  When the bit goes thru the other side, many times you will hear a 'pop' and see a small whiff of smoke when the bit comes out.  This is caused by the overheating of the oil and the rapid pressure drop causes dieseling.  In other words, a small explosion.  I've had this happen on numerous occasions.

   PlaneWood by Mike_in_Katy (maker of fine sawdust!)PlaneWood

2. 
   Kevin | Mar 06, 2004 10:48pm | #6

   Also, a vinyl sealer for lacquer might work.

   Vinyl sealer will work under poly too. It has a well deserved reputation akin to shellac's reputation as a good tie-in between disparate materials because most everything seems to adhere to it well. I use vinyl sealer for wash coats instead of shellac. I prefer it to shellac because of it's moisture barrier qualities. Although with a thin wash coat, the vinyl won't be thick enough to provide much of a moisure barrier. I personally don't like using vinyl sealer as a sanding sealer because it doesn't sand real well. But, it's handy and has a longer shelf life than shellac.

   The Independent Voter.com

   "Rather fail with honor than succeed by fraud" - Sophocles.

1. 
   OneofmanyBobs | Mar 07, 2004 01:54am | #7

   Actually, shellac is a great moisture barrier.  The dewaxed is a bit better than the waxy, and you do need to use dewaxed under poly.  The waxy will have adhesion problems.  Ready-mix shellac can have shelf life issues, but if you make your own there's no problem at all.  Alcohol denatured with methyl alcohol shortens the life and cheap alcohol sometimes has 10% water which is bad.  If you use SD200 or other alcohols with no methyl and no water, the shelf life is indefinite so far as I've found.  I've had shellac mixed for 5 years with no problem.   Methyl alcohol is pretty toxic and its best to avoid it wherever possible.  Particularly when you french polish or use it as a cleaner and have it on your hands and breathe it.  The lacquer products have some advantages, but the solvents are nasty and I don't have a spray setup that will handle it.  Shellac is pretty friendly stuff.  Does not sand very well either, unless you wet sand it.

1. 
   Kevin | Mar 07, 2004 07:10pm | #8

   Thanks for the feedback on shellac, Bob. I had never heard that about methyl alcohol and the shelf life of mixed shellac. Fine tuning via organic chemistry like that is a huge advantage to whomever knows how to do it, IMHO. As for shellac's moisture barrier qualities... I wasn't aware of that either. But, then again shellac isn't used much commercially and that's where the vast majority of my experience and knowledge is. I finish and paint in a commercial production setting for a living, which doesn't make me any more or less knowledgable... it's just a different sphere of the trade, so to speak. Where shellac is used commercially is as a pigmented stainblocker under latex and other house paints or as a tie-in coat between disparate materials that wouldn't normally adhere well to each other. I stock some pigmented shellac for just those purposes. But, that's really the limit of my experience with shellac.

   The Independent Voter.com

   "Rather fail with honor than succeed by fraud" - Sophocles.

1. 
   OneofmanyBobs | Mar 07, 2004 11:41pm | #9

   I think shellac has been unjustly left behind in the commercial world.  The catalogs and salesmen come and tout the latest and greatest synthetic.  None are perfect and few have any substantial history.  Shellac has been used for hundreds of years.  Environmentally friendly, nontoxic, versatile.  Cost per pound of flake shellac is comparable or cheaper than acrylic resins.  Can be nearly colorless to strongly colored.  True, its less consistent than engineered resins, but the chemistry is a lot less toxic.  As a sealer and binder for toners, I think there's nothing better.  It sticks to virtually everything.  Oily wood, other finishes, metal, glass, plastic.  Not as tough for use as a top coat, but still possible for some applications.  With all the concern about hazardous organics, I think its actually getting more popular again.

   Buy a can of varnish these days and you have no clue what you're getting without reading the MSDS.  Alkyd, soy, tung, polyesters, acrylics, urethanes, linseed, natural and synthetic resins, solvents, catalysts, driers.  I like shellac.  its simple.  It has shellac and alcohol.  You can play with the solvent a little or put in additives, but its basically simple and has a lot of performance for a minimum price.  It also keeps me further away from the highly toxic chemicals being used in the new finishes.  For commercial production where you have the facilities and safety features, OK.  For a small shop, I think a lot of the new stuff is just too dangerous.