Granite Fireplace, how do you clean rock?

[_RaT_]

I have a old granite fireplace. The rock goes from floor to ceiling. The previous owner covered the top half with a sheetrock wall and on the bottom he mortered on fake rock. I stripped it back to the granite. The bottom needs to be cleaned of a light coating of cement while the top is smoke stained from many years of wood fires. The granite is beautiful. Do you know of ways to clean up the granite? Acid wash? Bead blast? Wire brush? Thanks

 

[scott_vt]

I have a old granite fireplace. The rock goes from floor to ceiling. The previous owner covered the top half with a sheetrock wall and on the bottom he mortered on fake rock. I stripped it back to the granite. The bottom needs to be cleaned of a light coating of cement while the top is smoke stained from many years of wood fires. The granite is beautiful. Do you know of ways to clean up the granite? Acid wash? Bead blast? Wire brush? Thanks

Mornin RaT,
Muriatic acid can be used to clean rock and concrete. Caution needs to be used when using it both from the liquid itself and the associated fumes.

 

[Dozernut]

I cleaned our fire place stone by sand blasting it. I first built an enclosure out of plastic and taped all seams, then put on protective gear and went at it. Worked great, setup and tear down took longer than the blasting. I cleaned up the loose particulate with the shop vac. The fire place looks like new. We tried various cleaners but had no luck with them so we decided to sand blast. Good luck, Happy Holidays!

 

[Egon]

In your situation a sand blaster, powered wire brush or stone grinding wheel may be the easiest solution but still involve a lot of work.

 

[Dusty]

I'll second the sandblast method. Check with local stone masons as to what type of grit to use. It is a tedious job to set up the protective area, but well worth the work in the end. If the stone is smoke stained, you might want to investigate the chimney before going further to make sure that the fireplace is sound and safe. I had a stone fireplace in a cottage that never worked correctly. Upon closer examination, I found that rocks had come loose and had fallen down the chimney partially blocking it. There was no fix for this, so it just had to be removed. A lot of work went into building it, but the person that built it didn't quite know what he was doing.
Dusty

 

[_RaT_]

I'll second the sandblast method. Check with local stone masons as to what type of grit to use. It is a tedious job to set up the protective area, but well worth the work in the end. If the stone is smoke stained, you might want to investigate the chimney before going further to make sure that the fireplace is sound and safe. I had a stone fireplace in a cottage that never worked correctly. Upon closer examination, I found that rocks had come loose and had fallen down the chimney partially blocking it. There was no fix for this, so it just had to be removed. A lot of work went into building it, but the person that built it didn't quite know what he was doing.
Dusty

Thanks you guys. I suspected sandblasting or bead blasting would be the best. I intend to install a NG (natural gas) insert made by Valor. I will still have a wood burner elsewhere.

 

[GregMVT]

You might want to try Fantastik to clean off the soot. It worked really well on the bricks above the fireplace at my parent's house when I was a kid, long time ago!

Greg

 

[gotrocks]

Muriatic acid would be my LAST choice. The fumes from that stuff will rust any metal that will rust. Years ago we used it to clean new ceramic tile installations. The acid "eats" portland cement mixed mortar and grout.
We diluted it and used a brush to scrub the floor. Had a workman cleaning a new bath and he got "just a little bit" on the chrome lav. legs then turned on the faucet and flushed the commode...... had finger and thumb prints "etched" in all the chrome. That was when we had diluted the acid enough so at that time we did not use protective gloves, just bare hands with an acid brush. We lucked out; the home owner was a plumber and he agreed to replace everything labor free, we just had to purchase the damaged items.

 

[Jagmandave]

There are companies now that blast with dry ice, it's about the same cost as sand blasting but so much less mess, check into it. If there's no one in your area I have a source............

 

[gordon21]

CLR (calcium-lime remover) works like a diluted version of muriatic acid. It is in most big box stores for several dollars a quart.

Muriatic is cheap but VERY strong. Most jugs say to dilute it 10-1 or 20-1 before using on a project like yours. If you go this route, the cost will be under $20, but you will dearly pay for that cheapness by having to rinse and rinse and rinse and use a fan to blow the fumes out and buy some decent rubber gloves.

Muriatic acid=Messy, aggravating and cheap. But it will defintely work.