Okay, going to use acid/water to remove some white stuff on my rocks...help me!

[Cody]

Finally, after a few years, there is enough of white calcium (i'm assuming) buildup on my rocks at the waterfall. It's not a ton, but enough that I'm tired of looking at it.

I've read on the forums to try 5:1 water and acid, so that's what I'll do. A couple of basic questions:

1) what type of gloves should i use?
2) do i let it sit on there for a while, or do i use a wire brush right after spraying?
3) can i spray liberally or do i need to be careful with the amount I spray on?

 

[mknauss]

What are the rocks made of?

 

[Arizonarob]

Most likely gunite. I had the same thing on mine, and I had it bead blasted off with glass beads. So if it’s only on the rocks and not the entire waterline, you can try the acid. (Watch your water chemistry afterwards) But if it’s everywhere, you might want to look into getting it all cleaned up at once.

 

[Cody]

What are the rocks made of?

They are actual stones with mortar

 

[mknauss]

OK -- test the dilute acid on the stone in an inconspicuous spot. See if there is any effect. The mix will react with the grout.

Gloves, eye protection, a hose or bucket of fresh water nearby to wash it off your skin. It will fizz on the scale but some kind of mechanical action will be needed. If vertical, it will run off quickly so that will depend on how much you spray on.

Any that gets in the pool will effect the pH (and very slightly the CH) of the water.

 

[Cody]

Recommended type of gloves?

 

[duraleigh]

Stones will be tough to hurt. Too much acid will pit the mortar so rinse quickly after cleaning.

5:1 may not do much but try it first. Then go 3:1 and lastly, 2:1 but rinse quickly.

Acid will damage a wire brush. They make stiff bristle "acid brushes" for your purpose (at HD/Lowes)

Rubber gloves and SAFETY GOGGLES! A tiny splash of acid in your eyes quite painful.

If you have never worked with acid, consider asking someone with experience or hiring someone. It's easy enough but you really don't want to make any contact with it and you want to get it off the stonework by rinsing as soon as you get them clean.

The mixture should foam up pretty vigorously to tell you it is dissolving the calcium

 

[mknauss]

They will show acid resistant on the tag. Home Depot/Lowes carries them.

 

[Cody]

Thank you so much! Will head to Lowes and will report back on results...

 

[Cody]

bought gloves and spray bottle...could not find an acid brush and no one at Lowes was any help (ugh)....used 2:1 mixture. The area I'm working on is vertical, so once sprayed on it runs down quickly. I didn't let it sit too long for fear of damaging mortar. I used a wire brush i had at home, and it didn't do much at all. Lots of bubbling, but not a big difference at all. Ideas?

 

[mknauss]

That is pretty much the process. It does not look like much is done until the scale is all gone.

You either spend a lot of time on it, or hire some one to blast it off with kerserite or soda.