Acid etching wet cast concrete pavers?

[hiner]

We are experiencing difficulties acheiving a consistent acid etch on the surface of our pavers. Does anyone have experience with application methods for acidic solutions to pavers that will give an even overall texture? Both brush and spray applications have resulted in patchiness related to the time of reaction, multiple applications seem to make the problem worse. At the moment it seems to relate to the method of application rather than variations in the density of the face of the paver. All suggestions welcome.

 

[Ron]

hiner...the problem is not your application but the variable density of the pavers. They accept the acid differently so the response is different. If they have not coarse aggregate in them, that won't change. If they have coarse aggregate in them, etch until the aggregate is exposed. That will mask the variability.

 

[hiner]

Thanks Ron, we are after a fairly light etch to give a simulated natural stone finish, by the time we get an appropriate etch depth all over the face by reapplying we have large areas over etched. We need to avoid exposing the aggregate too much for the required effect. The patchiness appears visually to correspond with the timing and thickness of application rather than what you might expect to see from surface density variations.

 

[unclesyd]

What is your etchant?

I used a jelling agent and wetting agent in several etching jobs on concrete to apply different coatings, epoxies and vinyl ester.

 

[hiner]

We have trialed Hydrochloric acid, neat and diluted. Also a Hydrochloric based product with a fuming inhibitor, which also seemed to have the same application problems but without the noxious fumes. Do you etch wet or dry. How do gelling agents work?

 

[unclesyd]

A jelling agent works by increasing the viscosity and tackiness of the liquid. This in turn will slightly slow the action of the acid and help with keeping the etchant's action even. The wetting agent also helps keeps the action even.

I'm trying to find my information on tests with different acids or combinations we used.