I have French polished several pieces which were veneered with crotch mahogany. Crotch veneer always has microscopic cracks or at least larger pores, since some of the face is end grain. The pores were filled with traditional shellac and pumice stone dust (4f) and were initially transparent. A few months after completion, the larger pores have turned grayish white, and there is a haze over some areas. The piece has been in my diningroom, in controlled humidity the whole time. I spent two years making the piece and would very much appreciate any suggestions on how to rescue it. Other areas of the piece, eg the top, which is flat grain mahogany and satinwood inlay, does not have the problem. Thanks a lot.
Jay
Replies
Jay,
Has the piece been waxed? Pledged? Siliconed? Maybe try a bit of alcohol on a q-tip on an inconspicuous spot and see if that works.
sawick
I did use a thin coat of paste wax as a last step after French polishing, and machine buffed to a high gloss. There has been nothing else applied to the piece. Thanks for reminding me about the wax, but I think the whitening/graying is deeper. I think it is that the fine particles of pumice stone which were previously transparent, have become visible for some reason.
I know there was ample shellac, since the pores were filled with a traditional method. (cotton / muslin "tampon", charged with alcohol and 2 lb cut of blonde shellac, pumic stone dust sprinkled inside the muslin, which gradually permeates through the cloth and settles into the pores) I will try some alcohol, but unfortunately all the affected areas are conspicuousl - right on the front.
Jay
I'm not sure of the exact nature of the changes over time that go on with the french polish plus pumice grain filling technique you describe, Jayst, but it seems that eventually the pumice does revert to its original colour-- white. Pumice is usually added to the process to help level previous coats of polish and sometimes to fill the grain as part of the polishing job.
Plaster of paris used as a grain filler can end up looking white after a period of time too, and I suspect that in both cases the original whiteness at application is masked by ingredients in subsequent treatments which take a good while to evaporate out. Linseed oil sometimes used in the french polishing technique might mask the whiteness of both plaster of paris and pumice for a time-- but I'm not 100% sure of that.
Anyway, I'm not sure what you could do about the problem now except to strip off the polish and apply an aniline dye to the whole surface in the hope that this would be absorbed more or less permanently by the pumice powder as well as the exposed timber.
I tend to fill the grain entirely with grain filler prior to polishing, or use polish alone to do the same job. Each technique has its pluses and minuses. If I'm filling the grain with plaster of paris, I'll dye or stain the background colour of the wood, perhaps add a barrier coat of thinned out polish, and fill the grain with plaster of paris tinted with a water based powder paint, etc., followed by more polish. So far, I've not had any obvious signs of whitening come back to haunt me over the last 25 years or so, but over a longer 100 year or more period, I don't know what will happen for definite.
None of the previous paragraph helps you in your predicament, and apart from my earlier sugestion, I'm afraid I can't think of a good answer off the top of my head. By the way, I can't imagine that the wax thing is anything to do with your problem. Wax above a film finish is completely irrelevant what's underneath the polish. Slainte.
Website The poster formerly known as Sgian Dubh
Thanks for the input. In classic French polishing, the pumice dust, which is volcanic glass, should remain transparent indefinitely, since the particles are surrounded by shellac, in the pores. It's just like if you were to immerse fragments of broken glass in a glass of water. In any case, aniline dye is not an option due to the satinwood inlay and crossbanding, and holly string inlay. The piece was colored with potassium dichromate to chemically darken the mahogany, while leaving the holly and satinwood white/yellow.
Thanks,
Jay
The only problem with that theory is that I've never seen such a thing as glass clear pumice. Pumice is usually a brown/grey, or white, or close to white, whether it be a powder or in the form of stone, and eventually reveals itself as that colour if embedded in the grain or pores of timber.
I'm fully aware of how pumice is used in classic french polishing, as I was taught the technique many moons ago-- gawd, I'm getting old, ha, ha--- and as it is described by proponents such as Charles H Hayward. The trouble with Hayward, and many of his generation, is that he is guilty of passing on the bad advice he learned from generations of polishers before him. Much of what he says is useful, but on one or two techniques his advice is poor. Adding pumice to the french polishing techniques is one example, particularly when dealing with open pored or open grained timbers, such as mahogany, and one or two of his polish 'reviver' recipes are dodgy to say the least.
I suspect that the only recourse you have, now that you have revealed that there are inlays involved is to strip the polish as I said before, and attempt to dye the pumice with an aniline dye, but with the wrinkle that you'll have to carefully mask off the inlays with a layer of polish (or masking tape)carefully applied with a fine brush to prevent the dye bleeding into the inlay. It's inexact, and there's a good chance some of the dye will bleed under the polish into the stringing/inlay if applied with a rag or brush, and if you use a comparitively slow drying water based dye.
This creating a barrier to the inlays is again a traditional technique, and another way of imparting a hiding colour would be to lightly spray a dye or stain coat(s) [as needed] which is fixed to the surface of the timber by being mixed into a very thin coat of polish, either alcohol (shellac) or lacquer thinner (nitro cellulose based) and requires a sure touch, so some practice is called for if it's a new technique to you. Slainte.Website The poster formerly known as Sgian Dubh
I didn't mean to imply you weren't familiar with French polishing, but didn't know your degree of experience. Hope you didn't take any offense, none intended. Anyway, my additional question is whether in "stripping the polish" you have any idea of how to extract the pumice from the pores. Sanding really isn't an option due to the thin nature of the veneers, which have already been sanded. Jay
No offence was taken, Jayst. How could you tell what I know? I'm just an anonymous poster hiding behind a handle like most others.
I don't know of any way to effectively remove filler that's already embedded in the open grain or pores and sealed in with polish, except to wire brush it out or something else drastic-- which would destroy what you have. It's in their now, so all that I can think you can do is to hide it.
Something based on on one or two of the suggestions I made earlier will maybe help. It's a mess, and you're definitely in it, and it's just a case of making the best of a bad job. It's no fun, and I've been there and done that-- how do you say exasperated phut in a forum? Maybe raspberry covers it, ha, ha.
I guess the best you can make of it is to treat it as a lesson for the future. Avoid filling the grain of open grained timbers, such as mahogany, oak, etc., with 'white' filler mixed into polish, unless you're intention is to show white. For example, fill your mahogany with a tinted filler prior to polishing, or use the tinted filler between dying/ staining, an application of thinned clear polish to seal, followed by tinted filler, followed lastly by tinted or clear polish as needed. Slainte.Website The poster formerly known as Sgian Dubh
I appreciate the advice, but find it somehow hard to believe that French polishing should be abandoned totally. It has been used on mahogany for centuries and with pumice as the only filler. I have used Behlen por-o-pac filler (as an example of a tinted filler) in the past, and on pieces inlaid with contrasting colored (lighter) wood, you would blacken the pores of the satinwood crossbanding. This would look awful.
Also, por-o-pac hardens quickly and leaves a residue which is difficult to completely remove from the surface, especially along joint lines or in corners. If carvings are involved, it is virtually impossible to get off the surface completely, even with brushes supposedly intended for this purpose. It doesn't have the transparency of french polish alone.
Jeff Jewitt has written FWW articles and has a videotape of French polishing, where he actually recommends making up a thick paste of pumice dust and shellac, to be used as a paste filler before polishing with a tampon. I have tried this and it does work.
Yoiur further comments are welcome. I would especially like to know if you have a particular product you recommend as a pore filler for mahogany, with contrasting inlay or crossbanding.
Anyway, I may just keep the lights dim in the diningroom. So far I'm the only one who notices this problem. It drives me crazy, but everyone else thinks the sideboard is spectacular. Just shows what you can get away with.
Jay
Jay, I’m not suggesting that french polishing should be abandoned. The technique of using pumice as part of the polishing technique as a leveller and a filler has been used for a very long time, I agree. I’ve repaired quite a few antiques and British Victorian furniture. An extraordinary number of these pieces showed the pores filled with a white filler. The conclusion to be drawn is that this filler is either pumice, or some sort of plaster. Personally, I tend to think a white filler should be avoided in a dark timber, whether it’s naturally dark, or dyed/stained dark, unless the grain filling is intended to be white (or some other colour.)
You came up with broken glass in water being invisible as analogous to pumice powder in the french polish. To continue the analogy, if the water is drained off, the glass becomes visible again—a change to the masking agent has happened—in this case it’s gone. I think something similar happens with pumice added to shellac. Over time some sort of change that I can’t explain seems to happen to the french polish, and the white pumice always seems to become visible.
It’s difficult to decide how to approach the grain filling of veneered or inlaid work. Any filler (including proprietary filler such as Por-O-Pac) might get into the tiny pores in satinwood as you say. One trick, as I mentioned earlier is to mask such areas. Some apply sufficient coats of shellac over the inlay up to its edge bordering the field—this is my most common approach whatever type of filler I’m using. Some block it off with masking tape. Another approach might be to insert the inlay after the grain filling of the surround is complete. And yet another option is fill the grain entirely with polish. Proprietary clear grain fillers (Homestead Finishing for e.g.) are on the market too, but I’ve not yet used one to give an opinion. Each method has its advantages and its difficulties.
All the pore or grain fillers I’ve used can be a bit tricky to apply and to remove from the surface properly. Flat surfaces, or simple curved surfaces are easiest to fill and remove the filler. Mouldings and carved parts can be very difficult to handle, and some elect to leave intricately carved items unfilled completely, especially if they have deep recesses and crannies—that’s generally my choice.
Anyway, the commonly espoused method for applying and removing grain filler is to work across the grain. Almost nobody seems to mention burnishing off with the grain too, and also to use a fine abrasive nylon pad, again with the grain, a trick I get up to. Both tricks can remove those disfiguring cross grain striations left when working only across the grain.
Jeff Jewitt is a very knowledgeable finisher. I have to admit that I’ve never read any of his books, but I have read a few of his articles. If you have been replicating his techniques and you are experiencing problems, you could post your questions to his forum at Homestead Finishing—I can’t recall the URL, but it’ll be easy enough to find. He always seems to be helpful and I’m sure he would have some good ideas for you to try.
For myself, I consider polishing to be one of my weaknesses within the realm of cabinetmaking skills, and I’d take any advice you get from Jeff Jewitt over anything I say, ha, ha. There is also a particular poster that drops into this section of Knots that I recognise as having in depth knowledge on polishing subjects. If he drops in with an opinion, you’ll recognise right away (I did anyway) that he knows what he's talking about and he’s worth listening to. Slainte.Website The poster formerly known as Sgian Dubh
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