french polish problem

I am restoring a mahogany hall table using french polish and have a problem with the table top ,the legs, bottom shelf and carved centrepiece have finished beautiful. the top seems to have something bleeding through the finish after 24hrs. I have sanded back to bare timber washed the top with white spirits sanded with 400 grit then started the polishing process, 3 coats of orange shellac harden for 24hrs, then sand and3 further sessions with blond dewaxed shellac and grain fill with pumice. The finish looks great and approx 24hrs later the surface feels prickly and looks as though something in the pores of the wood has pushed up through the surface.I have done this process twice with the same result and am about to do it for the third time but thinking i may use thinners to wash it with. Any suggestions would be most welcome. Brit from brissie

Photos might help if you have them, or if it happens again. This is unlike anything I've ever heard of. My immediate assumption would be that the wood doesn't like the polish, but I think about a million pieces of polished mahogany furniture would say otherwise.

I would consider sanding back to bare, cleaning with a damp rag, waiting a few hours, sanding again at the finest grit, wiping with a damp rag again, waiting 24 hours, sanding again at the finest grit, wiping with a dry cloth, filling the grain, and then polishing.

Post updates if you make progress.

Cheers,
Luke

Luke , the problem doesn't show up on a photo. thanks Brit

Could it be silicon contamination after years of Mr Sheen?

If it is silicon, clean the surface thoroughly with Prepsol. We use this to remove silicon from panels before
painting or affixing vinyl signage.

Some questions first:

1. is this an antique piece of furniture?
2. If so, what was the condition when found?

if it was contaminated with something that could be your problem.

BUT

If it is not some oil or other contamination of old timber this actually sounds like a much simpler problem. If your shellac is dissolved in metho with a high water content, or the grain filler has a high water content, then the grain will swell with time - and produce a rough surface, and often also a 'milky' finish. Metho absorbs water from the air (hygroscopic) so old metho with a poorly sealed lid or cheap metho can have a very high water content.

If that is the problem then the solution is simple - better quality metho. If it is an antique i would also suggest that orange flake shellac is not the best - use a brown button shellac instead.

1.yes it is late victorian
2.it had been restored some 40yrs earlier ,grain filled with plaster then sprayed with lacquer and rosewood stain. It was crazed finish
OK i have been using a standard metho but this mix has been in the shop for a couple of months so the water contamination is possible. I have some garnet button shellac is that the same?
thanks John

I had a similar problem a few times, and I think I solved by wiping the high points off with a bit of steel wool or superfine paper, filling again with shellac (how ever many times feels right), wipe again with fine abrasive, then start the polishing again. My thoughts at the time was there was either too much oil in the polish initially and the rubber was too dry and or too thin.

Hi John,

Garnet button will be fine for Mahogany I would think - it is just a bit redder than the brown button. I would suggest using the same shellac from start to finish. For an antique I would not recommend a de-waxed shellac finish, the buttons contain a fair bit of wax, which works well for me here in Brisbane on antique furniture. Because the final finish, after the shellac has dried for a few weeks, should be a good furniture wax with a high Carnauba wax content (not just beeswax, which stays sticky and attracts dirt).

I hope that using better metho will help. If the grain raises then water is usually the culprit. If some chemical or oil is bleeding through it would form small bumps/lumps rather than raised grain.

If there is something that the former restorer put in the filler or the wood and it is now bleeding through the finish you may be able to clean it out of the wood with something like the Prepsol mentioned by Lappa above. I have never used that but I have used White Spirits/drycleaning solvent to try to clean old timber - with variable results.

One other suggestion, if you repolish as suggested and something is bleeding through, would be to try some patch experiments e.g. 1. let whatever is bleeding through harden on the surface and then lightly sand with say 600 grit. 2. try some white spirits on the lumps (without removing the shellac) and see if it cleans them off.

Good luck.

thankyou for all of your help.I resanded back to bare finishing with 400 grit then washed twice with thinners then restarted the process again using industrial metho from carbatec it has now been hardening for 3 days and is perfect.I think my problem may have been the metho but i have now converted and once again thank you. Brit