cleaning pool tiles

Need a little help with my pool tiles. These are the ones on the pool lip. They were originally light blue and had turned blackish with what looked like baked-on hard soot or grime. I've tried most of the tile cleaners and they were not effective.
Pumice seemed to do the job, however it was slow going and hard to get into the crevices (the tiles are "dimpled" to avoid slipping). What are my other chemical alternatives? Would muriatic acid do the job?
A photo is at: http://tinyurl.com/35b2s The light blue had a planter on top of it before.
TIA richard
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you asked this question last week so didnt anything work , you had all the options.
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snipped-for-privacy@webtv.net (m Ransley) wrote in message

My apologies for the double posts, I did find it. Lost it at first, since I could not remember when I posted it first.
regards, richard
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What you may have here is dirt attached to your tiles by stearates. Many chlorinator tablets, particularly the three inch diameter ones employ a metalic-stearate binder to keep them in tablet form like sodium, potassium or calcium stearate. These esters of stearic acid are soapy materials which are relatively insoluble in polar solvents like water. They accumulates near the surface where they carry surface borne dirt and dust to the tiles at the edge of the pool.
You may be able to remove it from the tile with a non-polar solvent like kerosene, or any other solvent that would dissolve greases or soaps.
The longer term solution is to get away from this method of chlorinating. Many of the 1" chlorinator tablets do not use stearate binders.
RB
r h wrote:

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