Stucco removal

Whats the best way to attack this situation? Stucco splatter on all exterior windows, spots as big as a quarter but mostly drops all over.

I’ve heard of the options but I need more information before pricing and attempting to clean.

What works?
muriatic acid
phosphoric acid

Phosphoric acid will be the fastest but since it is an acid many precautions need to be taken- sills,siding,skin etc. use caution around these areas to prevent damage.

Vinegar can work may take longer but is not going to damage other areas it comes into contact with.

If you are not familiar or comfortable working with acid dont be afraid to turn down the job. As many factors can cost you alot if a problem occurs.

I would check for some scratching prior to bidding also because usually the masons will try to wipe some off, scratching panes in the process.

They are old customers in a new house. I have already passed on the job, but would like to be more informed.

I did remove some of the splatter with a scraper on my 1st window, but there were tiny chips left. I didnt want anything to do with it.

Could you be specific with the Phosphoric procedure? What is the concentration? What do you use to apply? Do you have a hose on hand to rinse? How do you change your procedure when on a ladder? Tarps? Tape on frames/sills?


I apply full strength from squeeze bottle small amount as possible to cover area, flush with water from brush or applicator. Do not allow acid to dry on any surface, avoid direct sun to help . Use scraper as or if needed to assist removal. Some prefer horse hair brush to avoid mortar drag on glass to prevent scratching(I use regular applicator sleeve). I throw away applicator sleeve away after use with chemical.

Vinegar has worked for smaller areas but usually requires 2-3 applications to loosen mortar fully.

As far as ladder work same procedure.

If the builders dont require the mortar contractors to completely cover glass in the future I refuse to continue any further services.

Thanks for the help. Im in this situation too often. Ill talk to the owners and try and get the builder/stucco guys to take some responsibility, I might consider the clean only after i have my waiver written in blood. What about the whole tin etch haze thing, is it avoidable as long as the glass remains wet or is it with other chemicals?

I have not come across concrete on windows for a while but am looking forward to trying Safe Restore.

I also use a squeeze bottle but only with GG4 & use with a scraper. I find that a new blade, lots of dips in a bucket does the trick to get rid of debris. Strip washers tend to give you a nice white paint! Only after I’ve removed debris do I use the strip washer.

Phosphoric acid will not cause tin etch haze.

As stated previously, avoid use in direct sun.


Cement Off by Titan will work as well.

What’s average real-life dwell time?

Up to half an hour but this would vary w/ things like amount of material being worked on, temps, sunlight, etc.
I’d check each application after 15 minutes to determine if longer dwell times are required.

Do you have to keep it from drying?

Not from the times I’ve tested it. Of course I was using it on small spots.

I used Cement Off with great success a few weeks ago. Saved about $90,000 worth of Eagle aluminum clad windows. The windows were covered in mortar. The crew who did the construction clean up removed the mortar from the glass, but were unable to remove it from the window frames. You could see where they tried, and scratched the paint. The homeowner called me, and I was able to clean everything up with the Cement Off. I found that it worked great diluted 50/50 with water. I kept the mortar damp by reapplying every 5 or so minutes for a total dwell time of around 20-30 minutes. It turned the mortar into the consistency (and look) of paper mache. Then I brushed it off with a boars hair brush and WFP’d the windows, frame & glass.

At 50 dollars a gallon it’s a steal. I now have another very, very happy customer.

Great story Micah! If I may ask, how much did you charge to save your customer $90k?

Attaboy, Micah!

I’d reveal that in the Members Only area of WCRA, but not on a public searchable forum. Sorry. It was the highest residential invoice I’ve ever had though.

Sweet. Well do start a thread in there detailing that job! I would love to hear about it…

…see ya in NOLA!