I am a stained glass craftsman who will soon be reinstalling a stained glass window in a very large(16 foot round and intricately patterned rose pattern stone frame in a church. The stone is 100+ years old, of white to grey hue and is filthy with 100 years of candle soot which has been almost baked in by poorly placed heating ducts. I am unsure of what type of stone it is, but it is rough and granular in its surface texture further trapping the soot in its texture. I have been asked to clean it and wish to get an even thorough clean without doing any damage to the stone. Can you give any suggestions as to techniques, tools, appropriate cleaning products or solvents that will be helpful in cleaning this stone properly? Thank you very much William F. Dodds
Dear William:
There are solvents that could melt candle wax, but it takes lots of the suff and, even if the stone - probably a coarse limestone - would not be affected, before you're half-a-way into the job, you will start seeing colors even more beautiful than those of the stained glass window that you're about to install!... :-)
I would approach the job by steps:
1. You remove the worst of the wax with a 3" or 4" razor blade scraper.
2. You finish the removal of the wax on the surface with a very coarse grit metal-grade sandpaper.
3. If after this treatment the surface of the stone will not be completely cleaned, I would torch it using a plumber blow torch and, while still warm, I would keep sanding until I get to the bottom of the thing. Repeat if necessary.
If after all this treatment you will still have some staining, either the church will learn how to live with it, or you get back to me and I'll see what can be done.