Acid etching leaves more than a rough surface. It leaves salt residue in the pores, a weakened top layer, and often a blotchy pattern that no amount of polishing will even out. Polishing straight over it is the mistake that produces a patchy floor.

Assess the damage

Condition	Test	Response
Light etch, uniform	Water drop spreads slowly	Neutralise, hone from 100
Heavy etch, rough	Visible pitting, chalky feel	Grind 1-2 mm, then hone
Blotchy pattern	Uneven colour and texture	Deeper cut to uniform aggregate
Residue still reactive	pH strip above 9 or below 5	Neutralise and re-test before cutting

Neutralisation first

1. Vacuum all loose residue; do not wet it into the slab.
2. Wash with a mild alkaline solution to bring pH toward neutral, then rinse.
3. Re-test with pH strips at several points until stable.
4. Allow full drying before diamond work; damp cutting hides whether the cut is even.

How much to remove

For a light etch, one metal-bond pass at 30/40 followed by the normal sequence may be enough. For heavy etching, plan on removing 1-2 mm until you reach sound, uniform concrete. Check with a straight edge and a water drop; if absorption is still uneven, the cut is not deep enough.

Sequence after removal

• Metal bond to level, then 60/80 to remove the coarse pattern.
• Resin from 100-120 onward, with a densifier before the 400 step.
• Do not densify the etched layer itself; densify the sound surface you exposed.
• Finish at 800-1500 depending on the target gloss, and test slip resistance in wet areas.

Manage expectations

Etched areas often retain colour variation even after a uniform cut, because the acid attacked aggregate differently. Show the client a test panel before full production, and price the extra diamond consumption honestly. If the etch pattern is deep and the client wants uniform mirror, an overlay may be the cheaper route.