Asked on Apr 16, 2015

Salvage glass blocks

by Marla
I recently acquired a dozen glass blocks from my old high school demolition. How do I remove the -very hard and thick- grout/concrete that is on all of them. Is there a product or a method that has worked for anyone?
  12 answers
  • D & K D & K on Apr 16, 2015
    A reduced mixture of muriatic acid can be used to remove cement and grout from glass block but here's the caveat: "I do NOT recommend a / any DIYer attempt this". Some things are best left to professionals. It is extremely hazardous for numerous reasons and unless you're experienced in using this product I do NOT advise attempting it. Every conceivable precaution must be taken to prevent inhalation and all contact with the acid for yourself, the area and any and all bystanders, animals or wildlife that could happen upon the area.
  • Valerie Valerie on Apr 17, 2015
    I do not think that there is an easy solution. I have just tried to solve a very similar problem, and was told that soaking them in motor oil or cooking oil would help. Although it did loosen it, it was not really effective. I also tried putting them in boiling water. I found that this helped to a limited extent, especially after they had been soaked for several days. Ultimately I had to resort to manually scraping it off. I used as craft knife as that is what I had available. If you have access to a Dremel, I am sure that there would be an attachment that could be successfully used.
  • Nita Nita on Apr 17, 2015
    Not sure if this would even look good, but think about painting the grout , maybe a aqua color different shades.
  • Julie Julie on Apr 17, 2015
    I'm sorry I don't have a resolution for your question, but what do you plan on doing with them if/when you remove the grout? I have several old glass blocks I rescued from an old barn demolition and I'm not sure what to create with them....
  • Rus1058682 Rus1058682 on Apr 17, 2015
    I have used lime-away in a similar instance and a small wire brush. Just soak them for a few hours or perhaps a full day, depending on the age of the grout. Will not kid you, it takes a few repeats to remove it all but with a little luck and lots of scrubbing.. it should work.. GOOD LUCK..
  • Pete Wells Pete Wells on Apr 17, 2015
    I wonder if soaking them in vinegar would loosen the grout?
  • Fran Fran on Apr 17, 2015
    Have you tried a Dremel tool and grinding/cutting it off? You would need to wear a mask and protective glasses of course. I haven't tried this, but just a suggestion.
  • Trudy Trudy on Apr 17, 2015
    I'm thinking a combo approach. Chisel, dremel, hammer off the big chunks and then use the Limeaway.
  • Marla Marla on Apr 20, 2015
    The grout is about 3/4" on 2 or 3 sides. These were windows in a gymnasium. I plan on using the muriatic acid in a washtub when I get my courage up. I plan on using the blocks to fashion a light feature on our stone patio. Perhaps a 3-sided tower along a wall with a string of lights tucked into the open space.
  • Freyda Black Freyda Black on Apr 21, 2019

    So what worked best for the removal. I am contemplating buying used block and want to know what I am getting into!

  • Dmholt4391 Dmholt4391 on Dec 30, 2021

    A chisel and hammer.