Surprise White Stains on my Brick

This isn’t the same kind of a surprise as I found under the basement stairs.

I’m lucky enough to live near LimeWorks, which might be THE place to go for historic, non-Portland cement based masonry products and techniques in the United States. They’ve recommended a number of things for restoring my facade, starting with making sure I get at least 80% of the paint off of every brick and mortar joint. (I got there everywhere but at the very top where the bricks are laid in a dentil pattern.)

They also recommend that I take the whole wall back to lime-based masonry only. I was hoping this was what I already had. My mortar joints are tight and clean between the bricks, not slopped on the front, and they’re colored red. It turns out that I have an old but not original scrub pointing job. Here and there you can see the original mortar where the thin veneer of inappropriate Portland cement popped off. Getting it all is not happening this year.

They have appropriate lime-based mortar to repoint with and a specialty patching mortar for holes and other damage I want to repair (also not happening this year) but they recommend first going over it with waterglass, a mineral dissolved in water that dries glassy and binds damaged parts of the brick and marble. Just spray a light coat on.

Waterglass is a lot like glass, so if you get it on glass it’s really hard to get off. Knowing this, I decided to hurry up and get it on while I still have crappy windows I don’t care about. So I sprayed it on with a deck sprayer and…

Disaster

Have a closer look.

First off, I tried an acidic cleaner I have on hand hoping that the silicate residue would maybe be an acid soluble salt. It didn’t seem to work, but then it rained for several days and the stains look better when the wall is wet so I got my hopes up. When it stopped raining it looked as bad as ever.

Then I’ve been in touch with LimeWorks, EaCo Chem (the manufacturers of the best strippers and cleaners I used during the 4 months I spent restoring the brick I ruined in about an hour), and a friend who’s a chemist at DuPont.

It turns out that EaCo Chem makes a product they call Silicate Blush Remover specifically formulated to remove stains from silicate sealers that either puddled from being applied too heavily or that are failing. It’s a very week and buffered solution of caustic, or sodium hydroxide. Then my chemist friend texted back that “a simple caustic” would work.

So I wondered if it would make sense to use Stripper Cream, a caustic product I already own. This would be nice because I could do it Saturday morning and then proceed with the window replacement after.

My friend said that it would make them nervous to use something that includes potassium hydroxide as that might be too strong. Which was confusing because all my earlier research indicated that common lye (sodium hydroxide) was stronger and potentially more dangerous on brick. But apparently potassium lye is stronger in some cases, including dissolving silica. And since I want to take the surface bloom off without taking off everything I just put on, I’m better off with sodium.

So, I could look for common lye off the shelf and try diluting it myself. But it’s getting harder to find because it’s an ingredient used to make meth. And it’s really dangerous – remember when I burned a hole most of the way through the skin on my forehead using a paint stripper made out of DILUTED lye? I’m gonna feel safer getting it where someone else did the diluting for me. That means waiting until a local business special orders it, which means having to cover up my precious new windows when the time comes. But I feel like having to work for a half an hour with duct tape and scissors at this point is a real first world problem.