Replies

1. 
   jazzdogg | Nov 16, 2005 06:31am | #1

   Hi Dillon,

   There was a fairly recent discussion on this very subject not too long ago; you may have luck doing an advanced search of the "old" knots forum.

   FWIW, I'd spray.

   Good luck,

   -Jazzdogg-

   "Don't ask yourself what the world needs. Ask yourself what makes you come alive, and go do that, because what the world needs is people who have come alive." Gil Bailie

1. 
   dillon | Nov 16, 2005 04:19pm | #3

   Thanks for the reply. Unfortunately, my computer skills are less than my woodworking skills. I can't even find my way into the old "knots" discussions, even via Members Only etc...this new site is a bit frustrating, not to mention that my old "subscription" now entitles me to only 3 more months of Networking, when I renewed only in July.

1. 
   jazzdogg | Nov 16, 2005 07:20pm | #5

    

   View Image Finishing (Read-Only Folder) -  How to slow the drying time of shellac View Image

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   From: 

   shellacker <!----><!----> 

   Aug-31 1:48 pm 

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   25386.1 

   In his article "How to slow the drying time of shellac" (FWW #178,page 100), Chris Minnick recommends mixing equal parts of isopropyl alcohol with denatured alcohol in order to slow down the evaporation rate. OK, that would work because, as he says,  isopropyl alcohol evaporates about 25% slower than denatured ethyl alcohol. But I cannot understand why we should go to all that trouble. One can buy 99% pure isopropyl alcohol (NOT the standard rubbing alcohol) very inexpensively at the drugstore. Using only the 99% pure isopropyl as a solvent for shellac seems to work just fine. Is there some other reason (toxicity? longevity? hardness? moisture resistance?) why Mr. Minick wants to keep denatured alcohol in the mix? I would just as soon stay away from denatured alcohol anyway, because one never knows exactly which poisons or exactly how much of those poisons have been added in order to "denature" the alcohol. Does anyone out there have reason to believe it is worth the trouble of mixing different alcohols rather than simply using all Isopropyl alcohol? Thanks.

    

    

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   From: 

   byhammerandhand <!----><!----> 

   Aug-31 7:52 pm 

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   shellacker <!----><!---->

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   25386.2 in reply to 25386.1 

   see FWW 151 article by Jeff Jewitt. Below are his comments on shellac solvents:

   Thinner /Drying time /CommentsFor shellac: Pure gum spirit turpentine /Slow /Retarder: add one teaspoon to 4 oz liquid shellacIsobutanol /Medium slow /Retarder, difficult to find, strong odorIsopropanol /Medium slow /Retarder for brushing. May be sold as gas line antifreeze (check label)Denatured alcohol /Medium fast /Main solventMethanol /Very fast /Speeds up drying time. Difficult to find except for professional finishers

   Edited 8/31/2005 10:54 pm ET by byhammerandhand

    

    

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   From: 

   jackplane <!----><!----> 

   Sep-1 6:14 am 

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   shellacker <!----><!---->

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   25386.3 in reply to 25386.1 

   Add naptha.

    

    

    

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   From: 

   Pondfish <!----><!----> 

   Sep-1 6:51 am 

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   shellacker <!----><!---->

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   25386.4 in reply to 25386.1 

   I'd be leery of using just isopropanol (iPOH) as a solvent, because I'll bet the stuff you get in drugstores will pick up water quickly, or has too much already. But it certainly would be easy to test it out (and cheap)--go ahead and use iPOH for a solvent and compare the result to denatured alcohol (aka ethyl alcohol, ethanol, eTOH, or "alcohol" as in booze).  If it works as well, go for it.  But I suspect someone found long ago it didn't work as well because of the water in it, which is why we all pay more for denatured alcohol.

   Another poster recommended adding naptha.  That might speed up drying, it dries so fast.

   If brushing on the shellac is leaving too many brush marks, why not try padding on the shellac instead of brushing?  Padding works better with faster evaporation, and in my experience it leaves a glass smooth finish. It's fast to do, too, and you won't have to worry about slowing down drying times.

    

   Funny story about denatured alcohol from my school days... eTOH normally will not purify to 100%; it forms an azeotrope with water and the best you can do is get to 95% pure using standard distillation methods.  To make "denatured" alcohol, something else is added to the eTOH while distilling to prevent a water-eTOH azeotrope from forming. 

   When I was a wee undergrad doing histology, a couple of the women in the class thought it would be fun to make peppermint schnaps using denatured alcohol and peppermint sticks.  When someone made a comment in front of the professor about denatured alcohol schnaps, he quickly warned "Don't drink it! You could get leukemia because of trace amounts of benzene used from the denaturing process!!!"

   Never saw someone pale as fast as those two women in the class. 

   That said, I suspect benzene is no longer used in producing denatured alcohol, nor any other solvent with known carcinogenic properties.  So if you're worried about being around denatured alcohol, I would say that using care is prudent, but avoidance may be an over-reaction.  Still, it's a personal choice what kind of nasties you hang around.  

   Recommending the use of "Hide Signatures" option under "My Preferences" since 2005

    

    

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   From: 

   AlanWS <!----><!----> 

   Sep-1 8:23 am 

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   shellacker <!----><!---->

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   25386.5 in reply to 25386.1 

   My guess is that Minnick didn't want the shellac to dry as slowly as it does with pure isopropyl alcohol as the solvent, and that's why he recommended the mixture. It is possible that you can make a more concentrated solution (higher cut) when you use ethyl alcohol. The film you get should be the same, and if anything, shellac dissolved in pure isopropyl alcohol should have a longer shelf life than that made with ethyl alcohol.

   (For those who wonder about the basis of that statement: Shellac has carboxylic acid and ester groups. Deterioration in solution seems to involve esterification of acid groups, and possibly transesterification of linking esters by the ethanol solvent, to form derivatives that yield a softer film. The more hindered isopropanol should react more slowly.)

   Benzene is not used for denaturing ethyl alcohol. It was once used for making anhydrous alcohol (without the 5% water that remains after purification by distillation) but is not used for that purpose in the US any more. I think that methanol is the usual thing added to denature alcohol. It is toxic, and can cause blindness or even death if you drink enough of it, but it is not likely to cause a problem if you don't drink the dentaured alcohol, and ventilate as you use it.

    

    

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   From: 

   Biscardi <!----><!----> 

   Sep-1 1:54 pm 

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   25386.6 in reply to 25386.5 

   Isopropanol is toxic if you ingest or inhale too much.The methanol in the denatured isn't wonderful stuff either. I'd leave the isopropy alone if possible.

   Isobutyl alcohol is added to some of the proprietary solvents (Bekhol) to slow drying. I never found it that big of an improvement when padding. I am not certain if it would effect spraying shellac.

    I never had a problem with denatured evaporating too fast.

   Frank

   Edited 9/1/2005 4:57 pm ET by Biscardi

    

    

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   From: 

   Kevin <!----><!----> 

   Sep-1 4:32 pm 

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   shellacker <!----><!---->

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   25386.7 in reply to 25386.5 

   My guess is that Minnick didn't want the shellac to dry as slowly as it does with pure isopropyl alcohol as the solvent, and that's why he recommended the mixture.

   I think Alan's right about that. Someone else posted Jeff Jewitt's list of recommended retarders for Shellac which I would trust.

   My experience is more with nitro lacquer rather than Shellac. But, they're similar in many respects. Blending solvents, particularly a hot or "fast" solvent with a cold or "slow" solvent can be a huge advantage for the finisher. Using just a slow solvent can potentially lead to such problems as runs or sags in the finish. Using a blend allows the finisher to avoid some of the problems inherent in using just a fast solvent without running the risks inherent in using just a slow solvent.

   Essentially what a blend does for you is that the hot solvent evaporates quickly out of the finish which allows you to put more on, particularly on a vertical surface, without it running or sagging while the small amount of slow solvent in the mixture evaporates more slowly which keeps the finish material from skinning over too quickly... which is the chief culprit in overspray and orange-peel problems.

    

    

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   From: 

   shellacker <!----><!----> 

   Sep-2 2:04 pm 

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   25386.8 in reply to 25386.6 

   Thanks for responses. As anyone who has tried to sort out benefits vs. drawbacks of the various alcohol types will know, it is an enormously tangled & complicated subject, with a great deal of misunderstanding by end users as a result.

   From what I have been able to determine, Isopropyl Alcohol (I speak only of the 99% pure variety available in many drugstores--NOT standard rubbing alcohol which contains too much water for use in fine finishing) seems to be less hazardous to use than any other type available (except for pure ethyl alcohol which is difficult to obtain and expensive and which by its very nature would contain at least 5% water in any case).

   Denatured alcohol is highly inconsistent. While its main ingredient is ethyl alcohol, it must by law contain poison(s), but there is no specified recipe. The quantity and type of poison(s) is highly variable and usually not listed. It may contain large amounts of highly toxic methyl alcohol (I am aware of samples that contained 16%). It usually contains a small percentage of Methyl Ethyl Ketone, as well as other unappetizing ingredients like Ethyl Acetate. It will frequently also contain some isopropyl alcohol as well, the percentage varying wildly. Of course, the evaporation rate will vary according to the ingredients.

    

    

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   "Don't ask yourself what the world needs. Ask yourself what makes you come alive, and go do that, because what the world needs is people who have come alive." Gil Bailie

2. 
   SteveSchoene | Nov 16, 2005 06:40am | #2

   That amount of Bekhol will have a miniscule impact on the Seal Coat, especially if it already has been cut to 1 lb. with regular denatured alchohol--mostly ethanol.  Bekhol makes a small but noticable difference when you have mixed the shellac from flakes using only Bekhol as the solvent.  Seal Coat already has some additives to aid flow out compared to pure, mixed from flakes shellac, I think.   

   I'm not sure why it is necessary. Even entirely mixed with Bekhol you wouldn't expect to cover an entire panel before it dries. Using shellac is not like using varnish.    Shellac doesn't get applied and then tipped off.  It just gets applied in a single pass, and with thin  1lb. cut shellac an overlap or a skip makes little difference.   Next coat, the overlap will be a different place, etc.  You can't go back until the coat has fully dried.  About every third coat you can lightly sand out any defects  that remain.  The slower the evaporation the longer you have to wait between coats. 

   An important point is that if you sense even the slightest drag or resistance to the rag or brush you you stop immediately, in mid swipe.  Otherwise, you run the risk of  picking up previously laid coats, which gives a very nasty "rumpled" effect.  (Its not the end of the world, just let it dry fully and sand it out with no lasting impact.)   

   Personally, I'd just use shellac on an armoire, no varnish, and particularly no poly.  There is no risk of liquid water, or ammonia, and otherwise shellac is a good durable finish and rubs out very well.  And if there is a problem later, you can fix it in a wink.  Not so with varnish. 

    

1. 
   dillon | Nov 16, 2005 04:32pm | #4

   Thanks for the reply. I am considering only shellac, and I'll decide after I build numerous coats. My concern with the shellac only, even though my combo chest of drawers/armoir will be much too tall for anyone to put anything on (80"), last time I used shellac only on a refinished desk, no sooner had I finished than my visiting sister-in-law must have either put either a hot iron on top of a towel, on top of the desk, or spilled an alcohol drink, so I now have a big blotch that I'll have to refinish, again. Curious, why the strenuous objection to finishing off with a couple of coats of gloss wipe on poly, with a final coat or two of satin wipe-on-poly.

   I am also considering spraying, as jazzword suggested, with an HVLP that I have, but I am a little timid, especially with such a large piece (actually 2, that I'll assemble once I get it out of the basement!) that it may not be prudent and fumes may overcome my limited spraying booth that I set up in the basement with drop down tarps, but a fairly small window unit fan. (My children call the basement my "hole", and when I set up the 8X8 spray booth, I now have a "cave" in my "hole"!)

1. 
   SteveSchoene | Nov 16, 2005 10:07pm | #6

   No strenuous objection, though I don't think armoires aresusceptible of having a hot iron can be set down on them and it must be some party if an drink can be spilled an armoire.  The desktop is much more vulnerable and I would use a bit more protection there. 

   Any objection I have is not so much as to having a varnish topcoat, but rather it is to using poly for it.  If I did want a more resistant topcoat, I wouldn't use poly.   I would use a traditional resin varnish, either brushed or  thinned to make it a wiping varnish.  Any varnish thinned with mineral spirits can be thinned to what ever degree you want.  Those resins will provide substantial protection, but look clearer, and be easier to rub out if you need to.  Save poly for floors. 

1. 
   dillon | Nov 16, 2005 10:30pm | #7

   Thanks for the reply. I am always open to suggestions/advice, and had more or less settled on the MinWax Wipe-on-Poly based on the FWW #178 article by Minick. Within the constrainsts of the Network for advertising, etc...would you have a recommendation for your alternative, wipe-on-varnish?

1. 
   SteveSchoene | Nov 17, 2005 02:27am | #8

   I like Waterlox sealer/finish for a nice medium gloss.  It can be used without much if any additional thinning.   There are also Satin and High Gloss versions.  The high gloss would need quite a bit of thinning.  Pratt & Lambert 38 is a nice, light colored varnish, based on Soya/Alkyd.  It comes full strength, and would need a good bit of thinning to wipe-on.