efflorescence on mosaic on concrete planters

[Ron]

Hi Julie,

In my experience, a mild sulfamic acid and water solution is fine for glass tiles and grout. Use a thick, white Scotchbrite pad (or go to Home Depot's rental section and buy a big square pad of it that is sold as pads for floor machines and cut into 6x6 squares) to apply it and scrub it. Leave it on a few minutes (2-3) and rinse well with clean water and sponge. Dry with towels to remove any residue. Timing and rinsing is important to prevent etching and damage to the tiles and grout. Works for me every time.

[jerrymlr1]

I believe the acid won't affect the glass at all other than clean it. I have had glass mosaics sit in a bucket of acid for months (forgot about them) and the glass was fine. Anytime I rinse tile with an acid solution I follow up with a baking soda and water rinse to neutralize the acid and then rinse with water. Nice planters.

[jmuellejans]

Update:
Friday we removed efflorescence from all 7 planters (126 squ ft) using a diluted white vinegar solution and a lot of scrubbing. They are shimmering once again.

We waterproofed the inside of the mosaic planters today.

I want to prevent water from seeping into the top edge of the planters when we have heavy rains. In June, we built up the rims on the planters and beveled the edges with thinset mortar, then added a layer of grey sanded grout, to match the grout lines on the mosaics.

Questions:
What will effectively make the rims waterproof?
How best to apply?
I am going for more than water resistant on the grouted rims if that's possible. My goal is to prevent water from soaking into the planters through the rims. I hope this step will prevent further water seepage through the grout lines and prevent further efflorescence from occurring on the glass tiles.

Thank you for your time and suggestions on this atypical tiling project.

Here are photos showing the top rims on two of the planters

[jmuellejans]

Hi Jerry and Ron,
Thank you for confirming that weak sulfamic acid would be OK on the glass tiles based on your experience. I was unsure how to mix the Drylok Etch sulfamic acid crystals to create a weak acid and could not find out any info on percentages. If you read my previous post, you will see that I decided to go with diluted white vinegar (2.4 pH at full strength). I found full strength was too much (grout started to lift off). a 4:1 vinegar to water mix worked best, weakened the mineral salts but not damaging the grout. The Drylok Etch sulfamic acid when mixed as instructed was 1.8 pH which would have been too strong. I decided to err on the side of caution.

When you say "weak" solution of sulfamic acid can you please provide specific details on what you use and how you mix it?

The white pads are gentle on the glass but I ended up switching to green Scotch Brite which worked very well and did not scratch the glass (I work out but am not a powerhouse of strength by any means. It's all relative, as I am learning in this forum!)

If you read my previous post you will see my next "pressing" questions about waterproofing grout, which I hope to tackle in the next day or so. This has been an amazing project, full of surprises. I sure am learning a lot and hope to make more mosaics in the future.

Thanks for the +++ feedback on the mosaics. My student and I collaborated on the concepts and imagery. I synthesized their ideas into a set of seven designs which we created this past spring.

[Ron]

Hi Julie,

Wow, those planters look so good!

Great idea to bond the grout on the rims with tile mortar.

I use this cleaner often:



For something like your application, I'd have mixed about 3 oz (0.2 lbs) into a gallon of water and scrubbed it with white nylon pad.

To treat the grout you can't go wrong with this product:
http://www.drytreat.com/sealers/residential/40sk.html
That will repel water. Sealing it up entirely with a marine varnish or similar will alter the look and may lead to efflorescence again.