Wetter is Better (November 2007)

Unfortunately, I can’t give them a quick-and-easy answer. Contrary to popular belief, it’s not because I’m a jerk; rather it’s that for every rule in the stone business, there’s an exception. And it’s the one principle that keeps me interested and focused on learning more and more about stone every day.
I can, however, tell you after years of research (and frustrating experiences) that when it comes to polishing – generally –  wetter is better.
“You mean there’s a dry-polishing process?” you ask. Yes, there is, and aside from being somewhat quasi-harmful on your lungs, it does have a place.
First, let’s try to get a basic understanding of how compound polishing affects marble. (This article is dealing mainly with marble and limestone polishing.) Although some techniques will be similar, there are different principles at work.
Because marble is acid-sensitive, many powders or pastes used in the finishing process employ acids to enhance or quicken the effect of the abrasives contained within. The whole purpose is for the fine abrasives to smooth out the microscopic scratch pattern created by the diamond abrasives (or by wear if not a final step to honing/restoration).
Powder polishing won’t remove scratches or etches. It can and will, however, disguise them so they’re not noticeable. To truly remove a scratch or etch, you must remove the stone around the indentation and feather it back. The compound process will bring the dull color of the stone in these trenches and divots back to an even look and similar gloss.
How this all takes place is somewhat of a mystery (even after a long and detailed explanation), but I can tell you one thing I have noticed: Since I have seen a number of companies adding shellac to their formulas for “lubrication,” I’ve seen dramatic results in the use of these products.
Now, why even consider a dry powder?
It was brought to my attention a few years ago (by a manufacturer) that employing a dry powder for polishing would be advantageous because it was simple, and any technician could easily do it. Vanity tops would be a breeze because you no longer had to fear water spraying everywhere from 600+rpm machines, and protection of surrounding surfaces was therefore no longer an issue.
The simple theory on dry-powder polishing is this: Since most powders are acidic when added to water, the more water you add, the hotter (more acidic) the acid becomes. If you can control the level of acidity by the amount of water you employ, you can more easily polish the truly difficult stones, like Negro Marquina.
How is it done?
• Sprinkle some powder on the surface, in an area the size of the pad you are using, like Parmesan cheese.
• With a spray bottle, just add a little bit of water – enough to make a light paste.
• Work the paste back and forth until you see the desired gloss.
• From there, adjust the amount of water or powder to the stone, depending on the results that you see.
When shown how to use this process in a factory or controlled setting, it looks very easy. In the field, it can have its drawbacks.
First, you have to learn how much powder and how much water for each stone. This can get difficult when dealing with employees who don’t want to think.
Second, the paste created in the process can, and will, get glued into any recessed grout joints and (on occasion) can bleach out color, causing a dark grout to look grey. This isn’t a problem for white grout, because most powders are white, but try this on a black or brown grout and see how fast you collect payment.
A third area of concern (even with white grout) is that, when washing the floor after polishing, excess compound stuck in the grout joints can dislodged and – because of the acidic level of the compound – etch the finished stone.
Notice, however, that I mentioned that two-thirds of the problems involved grout. On vanity tops, where grout is rare, a mostly dry-polishing system can and will be appreciated. Also, on walls, it helps to keep your spray down to a minimum.
You just need to be aware of the dangers (and added work) that going dry can create. Dry-powder polishing is OK on slab polishing, but wear lung protection, since the dust created is harmful.
The wet-polishing process, for me, had a steep learning curve. Years ago, before Vic Green came up with a paste compound, the only powders available for marble were either too hot (acidic) or too cold, which took forever to get results.
The hot powders did a great job in the work area directly, but the slurry splash would etch anywhere it landed. This would create a need to go over areas several times to blend in the finish. Also, on certain stones, like Negro Marquina, the hot powders would dull-etch the already diamond-treated finish.
Today, there are several similar polishing compounds on the market that can be used wet and, when used properly, are fairly simple (even for the MP3-wearing, low-wage technician). The secret is in the proper procedure and careful following of instructions.

Required Tools
Tape/plastic
Floor Machine with Velcro® drive block
Wet vacuum with good squeegee wand
Feed water and “hot mop”
Rinse water and mop
Compound
17” white/natural hair pad
An assistant

Procedure
• Tape the surrounding area to protect from honing slurry.
• Wet a small workable area (4’ X 4’) and apply scoop of compound to center.
• Place machine with white-nylon or hair pad on compound and work in tight circles, keeping slurry in the center.
• Work slurry to next 4’ X 4’ area, and have the assistant use the squeegee to move remaining slurry to new area.
• Add water and/or compound as necessary.
• When proceeding to new sections, wet down finished area with “hot mop” (one that touches compound) to neutralize and rinse.
• After working 200-400 ft(2), take your machine back over the finished area (while still wet) to loosen any compound from edges, cracks or grout joints. Have the assistant vacuum completely and then rinse with a clean mop.
• When finished, ensure that all moisture is removed from floor, and buff with a new white nylon pad to remove any residue. A 0-grade steel-wool pad can also be employed, but always ensure that there’s no moisture as this could cause black oxidization and turn parts of the stone dull and/or black. Also, all residual metal fibers from the steel wool need to be vacuumed up to prevent rusting and oxidization.
• Remove tape, and store equipment after cleaning.
If followed carefully, you can successfully polish every marble you come across with this process. The secret is in keeping the area wet and going over it a second time without adding compound. This second sweep loosens the compound, and also enables you to blend in any light etch marks created by slurry spray.
Also, working small areas allows your compound (and the acid contained in it) to work with the abrasives. Try too big of an area, and you’re only getting the abrasive action – and not the assist of the acid (or vice versa).
The white or natural-hair pad is used, instead of red, to prevent any color bleeding from manufacturing dyes.
This process works great on floors. On walls, however, you need to be aware of where the slurry’s going to spray. Counter-top polishing can employ this method if you can contain the water.
I like the new compounds that are on the market today that can be used wet. It’s a Tom Rule: Wetter is better!
Whatever process you adopt, ensure you wear the proper safety equipment. And, remember one handy, hard-learned tip … always work towards the exit.
Tom McNall is founder and owner of Great Northern Stone Care, a Huron Park, Ontario-based stone-cleaning and -restoration company servicing all of southern Ontario. He also serves as the director of training, technical assistance, and operational support for Stone Restoration Services, a division of Stone Shop International. Tom offers corporate and private consultations, serves as a trainer for the Marble Institute of America, and is also on the organization’s board of directors.