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T.Hoffman
04-19-2012, 02:01 PM
Here at work we were able to snag a beautiful 24x18 Starrett AA granite surface plate.

Only thing is that it seems to have aluminum residual marks on it.
They are not scratches, but "lines" of aluminum on the surface.

I have some granite surface plate cleaner from McMaster, but that did nothing for the aluminum marks.

Any suggestions for removing those marks?

Forrest Addy
04-19-2012, 02:18 PM
We're talking streaks of aluminum like smeone dragged an aluminum casting over the surface and it left an indelible mark. Aluminum is attacked by lye and ammonia both chemical "bases" (as opposed to acids). The base will etch the aluminum out of the granite matrix. But beware: use it sparingly. Some minerals in granite are attacked by chemical bases like hydrated ammonia.

I suggest ammoniated glass cleaner. If that doesnt work try a little sodium hydroxide solution in a Q tip. This may leave dull straks on the plate and may loosen mineral particles. Try it on a corner before you commit to attacking all streaks.

The streaks don't hurt the plate's function. The problem is purely cosmetic. While appearances count, this is a surface plate. Preserving its flatness and finish takes precedence over appearance. You may have to live with the streaks. If it's REALLY important to you get the plate lapped and calibrated. The lapping done by the cal lab technician will take out the aluminum streaks and restore the pristine surface.

goose
04-19-2012, 02:27 PM
Try Bon Ami cleanser. It's an abrasive, but very mild, and will break down quickly. Hasn't Scratched Yet...

Dr Stan
04-19-2012, 03:33 PM
Try Bon Ami cleanser. It's an abrasive, but very mild, and will break down quickly. Hasn't Scratched Yet...

Bartender's Friend is also quite good.

Have you tried marble or granite kitchen counter cleaner?

T.Hoffman
04-19-2012, 03:41 PM
Thanks for the suggestions!

Haven't tried anything yet outside of the granite plate cleaner stuff, didn't want to use something that could cause harm to the surface.

Seems to be purely cosmetic, I might just leave well enough alone for now.
But I tend to be anal about having things clean and nice....

macona
04-19-2012, 04:08 PM
Windex works.

gwilson
04-19-2012, 04:32 PM
Bartender's Friend has oxalic acid in it. I don't know its effects on granite. Since oxalic acid is a poison,I'm surprised it is readily available to use. I'd use nitrile gloves if I used it myself. Maybe I'm over cautious?

Dr Stan
04-19-2012, 05:51 PM
Bartender's Friend has oxalic acid in it. I don't know its effects on granite. Since oxalic acid is a poison,I'm surprised it is readily available to use. I'd use nitrile gloves if I used it myself. Maybe I'm over cautious?

Yes I wear gloves as it tends to chew up my skin, but it sure does a good job of cleaning. BTW, I wear gloves on a regular basis when using any kind of cleaning product as they all tend to attack my fingers and cause nasty splits.

oldtiffie
04-19-2012, 06:30 PM
+1 Forrest.


We're talking streaks of aluminum like smeone dragged an aluminum casting over the surface and it left an indelible mark. Aluminum is attacked by lye and ammonia both chemical "bases" (as opposed to acids). The base will etch the aluminum out of the granite matrix. But beware: use it sparingly. Some minerals in granite are attacked by chemical bases like hydrated ammonia.

I suggest ammoniated glass cleaner. If that doesnt work try a little sodium hydroxide solution in a Q tip. This may leave dull straks on the plate and may loosen mineral particles. Try it on a corner before you commit to attacking all streaks.

The streaks don't hurt the plate's function. The problem is purely cosmetic. While appearances count, this is a surface plate. Preserving its flatness and finish takes precedence over appearance. You may have to live with the streaks. If it's REALLY important to you get the plate lapped and calibrated. The lapping done by the cal lab technician will take out the aluminum streaks and restore the pristine surface.

Forrest's last paragraph is the kicker.

If it were me I'd leave it "as is" as accuracy over-rides all other considerations - absolutely.

But get a cost on lapping and calibrating first - but sit down when you get the cost.

Add travelling/transport costs as well.

oldtiffie
04-19-2012, 06:45 PM
From Starrett:


5) How often should I clean my surface plate?
A) This depends on how the plate is being used. If possible, we recommend cleaning the plate at the beginning of the day (or work shift) and again at the end. If the plate becomes soiled, particularly with oily or sticky fluids, it should probably be cleaned immediately.
Clean the plate regularly with Tru-Clean or Rahn Waterless surface plate cleaner. The choice of cleaning solutions is important. If a volatile solvent is used (acetone, lacquer thinner, alcohol, etc.) the evaporation will chill the surface, and distort it. In this case, it is necessary to allow the plate to normalize before using it or measurement errors will occur.

The amount of time required for the plate to normalize will vary with the size of the plate, and the amount of chilling. An hour should be sufficient for smaller plates. Two hours may be needed for larger plates. If a water-based cleaner is used, there will also be some evaporative chilling.

The plate will also retain the water, and this could cause rusting of metal parts in contact with the surface. Some cleaners will also leave a sticky residue after they dry, which will attract airborne dust, and actually increase wear, rather than decreasing it.


at:

http://www.tru-stone.com/pages/faq.asp#question5

John Stevenson
04-19-2012, 06:53 PM
Best way to get marks off Tiffies plate is photoshop.

mike4
04-19-2012, 07:02 PM
Nah , just chuck it on the surface grinder and go at it .

Seriously ,
Whats a few alumininium stripes going to do to any measurenents anyway they wouldnt be able to be measured by 99% of people .

They are purely cosmetic dont panic.
Michael

oldtiffie
04-19-2012, 08:09 PM
Put a cover over the plate unless it it being used - or else as some seem to do - just use it as storage or bench space, cover it with junk and it will never be marked again - if you can find it.

oldtiffie
04-19-2012, 08:11 PM
Nah , just chuck it on the surface grinder and go at it .

Seriously ,
Whats a few alumininium stripes going to do to any measurenents anyway they wouldnt be able to be measured by 99% of people .

They are purely cosmetic dont panic.
Michael

Do you think my cosmetic removal stuff (in our bathroom) will do the job?

No?

It doesn't do me much good either (no surprises there).

Rosco-P
04-20-2012, 07:52 AM
Best way to get marks off Tiffies plate is photoshop.

That takes too much time. Just "bin" it! Buy a "far East" plate with a bogus inspection sheet signed by HuFlungDung.

oldtiffie
04-20-2012, 08:30 AM
Nah.

As JohnS suggests in his infinite wisdom, I'd "shop" it and cover the entire plate with it.

I must choose my colours carefully to go with my carefully structured decor plan for the shop.

Perhaps I should cover it with Prussion Blue scraping paint - that orta throw 'em.

Or perhaps cover it with some of that dung that is getting thrown about by Who (or is it Whom?).

Perhaps I could grow a garden on it - with "Forget-me-nots"

John Garner
04-21-2012, 01:45 AM
Try a soft pink pencil eraser to remove those streaks.