# problems polishing granite



## bkb0000 (Feb 1, 2009)

i've been doing a little granite and marble over the last year- maybe 5 or 6 big jobs requiring some form of polishing, each with dark granites- absolute, quite a bit of pear blue, galaxy, etc. had great results so far. i have an alpha variable speed wet grinder with 2 sets of 2 diamond pads, one about half worn, one brand new and freshly opened up.

decided to give granite slab a try- in my own house first: got a big slab of pre-polished 3cm butterfly blue, cut out the sink, scuffed it a little with this new corner cutter i'm not used to, so i decided to polish it out.

here's what i have now: an 8x2 slab of granite with about 4" of that completely dull and cant get it to polish out. why mott the hoople? never had granite refuse to polish. the butterfly blue is cheaper than most (all) of the granite i've worked with so far, and more porous, but the un-dicked-with section is bright and beautiful shiny.

here's what i've done: cut out sink, roundovered the cutout, polished the roundover, noticed some surface scuffing from my new tool around the sink. started with 400 to rub it out, it rubbed out fine, moved to 800 and the pad stuck to the slab- its a well used pad, still has some tread on it, but it's like it's made of rubber... lots of friction, bogs down my grinder. turn up the speed and water WAY up, move to 1500 which behaves fine, 3000 runs smooth- dry everything off and it's all dull and hazy. i assume my 800 didn't do the job, it looks like it stopped polishing at 800. open up the pad (thinking i might have run it dry at some point), same problem. so i bought a new set of pads, opened them up real good, and try again- same problem.

switch to a fresh chunk of scrap- start with 200, dull it up, work through all the pads, new and old, still cant get it to gloss up. i started to work backward and try some reverse-engineering, and haven't yet gone back behind 3000- i apply 3000 to polished area and it stays perfectly polished, so it snot the 3000. gotta drop back to 1500 and try to polish it out, then 800, etc- is this the correct course of action? and what do i do when i find the pad that's holding me up?

what am i doing wrong?


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## bkb0000 (Feb 1, 2009)

the odd friction of the older 800 grit was cured by opening, BTW. that's not the issue anymore.


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## Floordude (Aug 30, 2007)

Two grits??

Your skipping too many grits to take the scratches out.


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## bkb0000 (Feb 1, 2009)

i didn't skip any- 400, 800, 1500, 3000 on two different sets


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## wellbuilthome (Feb 5, 2008)

I have the same set up , It hard to get the granite perfect after it gets scratched . I try not to run the tool over the edge of the grind . The best thing Ive done is to get the scratch out first, then start polishing lightly use a little presser for a longer time . clean very good between grits. To remove the hayes at the end i have a fine powdered diamond that you use to get the finish shine with the polisher .( It wont be perfect )John


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## Dan V. (Oct 16, 2008)

I've had similar issues when polishing edges on Black Galaxy. You need to drop all the way back to 50 or 100 to get the scratches out. Low RPM (1500 max), plenty of water and don't be afraid to apply some pressure. As you progress through the grits, you need to feather out your working area. Using a wax marker, make concentric circles (or half-circles in your case) around the scratches and as you to move to each higher grit, move out to the next line.


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## StoneRenew (Feb 26, 2009)

Granite polishing is very tough. You say you have polished Black Galaxy? But you can't polish this one?? Doesn't make sense to me. Black Galaxy is probably the toughest granite out there to polish because of the dye's and agers used when its Fabricated. With most dark granites you have to take it up to 8500 grit. It could be that your using the wrong kind of pads. Usually I dont go to resin till about 1000 grit. You also might want to try polishing with Tin Oxide for a final buff. What pads are you using??


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## StoneRenew (Feb 26, 2009)

Floordude said:


> Two grits??
> 
> Your skipping too many grits to take the scratches out.


He isnt skipping grits.


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## So Cal Chando (Jul 21, 2009)

go all the way back down to 50 grit take your time make sure its smooth after every grit... use a polishing wheel.. and if that doesnt work u can use like a laquer.. "tiger ager" its used by the shops down here....


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## Bill_Vincent (Apr 6, 2005)

My understanding is it's next to impossible to properly spot polish using a 4" polisher on a flat surface, like on a piece of slab or tile?


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## GraniteGirl (Sep 1, 2009)

Hi Bill!! How are ya?! :thumbup1:

Surface polishing is possible - with a lot of practice and the correct tools.

High quality resin pads like ALPHA or comparable brands, along with rigid polishing disks (also ALPHA, although a few others do exist) are vital to the process, along with a high quality buff pad suited to the color (light/dark) of the stone you are polishing.

You will need a variable speed machine and loads and loads of practice and elbow grease.

Suffice to say, not many DIY persons or folks that are not dedicated stone professionals are willing to spend the money or time to learn to do this properly. The initial outlay (cash wise) could end up being $400-$500 depending on the quality of your tools & pads. The rest really takes hours and hours of trial and error to perfect.


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## Bill_Vincent (Apr 6, 2005)

Hey Lady!! Nice to see you found your way over here!! :thumbup:


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## brzelt (Jun 10, 2006)

Is this granite acid sensitive?


From your description, I question whether you have a basalt or a true granite.
Most basalts (cheap chinese dyed 'granites') are almost impossible to polish plus
they are acid sensitive like most marbles.


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## bkb0000 (Feb 1, 2009)

StoneRenew said:


> Granite polishing is very tough. You say you have polished Black Galaxy? But you can't polish this one?? Doesn't make sense to me. Black Galaxy is probably the toughest granite out there to polish because of the dye's and agers used when its Fabricated. With most dark granites you have to take it up to 8500 grit. It could be that your using the wrong kind of pads. Usually I dont go to resin till about 1000 grit. You also might want to try polishing with Tin Oxide for a final buff. What pads are you using??


I've never surface polished black, just the roundovers, which seem to be significantly easier than surface polishing. you could be right about the pads, they're not super expensive pads. they work great for roundovers, and i have surface polished several marbles and a couple granites with great results with them. this butterfly blue doesnt seem like it should be any harder to polish than blue pearl, with is obviously denser- that stuff took some elbow grease but came out really well. those were pieces that had swirl marks in them- all the supplier had from the same lot when i ran short.

but, as i said, i've never done slab/this big of an area before.



So Cal Chando said:


> go all the way back down to 50 grit take your time make sure its smooth after every grit... use a polishing wheel.. and if that doesnt work u can use like a laquer.. "tiger ager" its used by the shops down here....


i did what you say a couple times.. same results. in fact, it seems the more i take off, the harder it is to get back up- the left side of the sink cutout, where i did take it all the way down to 50, is noticeably flatter than the right.

i did finally resort to lacquer... this is getting into totally alien area for me, but i did already have some stone lacquer from another project. it was just too damn hard to get an even coat over the whole thing. i tried twice, stripping off both attempts. i wasn't really trying all that hard, though- i suspect the best application method is going to be a one-swipe application, like with a 2" floor finishing bar (which i have). i just figured this was a stupid idea to begin with, and gave up. but if you've done it/know it works, then i might explore that further..



brzelt said:


> Is this granite acid sensitive?
> 
> 
> From your description, I question whether you have a basalt or a true granite.
> ...


i don't know- i've wondered since the beginning if i just have really crappy "granite." it was sold to me through an outlet place that gets these from strange origins and sells mostly to local distributors (they say). all their stone products are seconds or thirds, which, in the right application, has worked fine for me in the past. is there some kind of test to see? and if this is the case, is it reasonable to assume it came with some sort of lacquer/resin/something that i stripped off with my polishing attempts?

thanks for the replies, gentlemen. and ladies.


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## docrock (Jun 5, 2013)

brzelt said:


> Is this granite acid sensitive?
> 
> From your description, I question whether you have a basalt or a true granite.
> Most basalts (cheap chinese dyed 'granites') are almost impossible to polish plus
> they are acid sensitive like most marbles.


Hi everybody! New user here....not new to the granite industry though. 

I know for a fact that you cannot hurt black galaxy with acid. I have used undiluted muratic acid directly on the surface of several granites to test its resilience. It does not seem to harm the surface at all. DO NOT PUT ACID ON MARBLE!!!!

Black granites are the most difficult to polish without a doubt. From my experience, you must take twice as long with each successive grit. I reduce the amount of water I am using litle by little after I am finished with 800. Be very careful not to allow the pad to go completely dry while polishing because you will "burn" the stone and turn it white. The object here is to crystallize the surface without changing the color. That is how the surface becomes very shiny. I go to 5000 grit with diamond pads and then use a compound called Diaglo. This is a powder that you mix with water to a toothpaste consistency and polish the face with a felt pad. Start in the center of your problem area and polish in small circles with your rpm of your machine very slow and work your way to the outside. You should work the coumpound until it turns back into a powder and then continue polishing until it disappears. It takes a very long time and sometimes it is better to buy another piece than to spend the time on it. 

I have used Ager Tiger before, but I find that it is to thick and will not penetrate the stone. Try the standard Ager. Use it after about 800 after the stone is completely dry, then let it cure for 24 hours and finish your polishing process and apply the ager again to the entire surface. 

Good luck!


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