Rick --- Ratios vary depending on the mix to be etched and time. We use full a strength dip on commercial work, but only for about 30 seconds, then a clear water wash followed by a dip in water with baking soda to neutralize. Generally speaking, the stronger the concentration, the shorter the exposure required to acheive a given etch. Likewise a 50/50 solution will be less aggressive, so you leave it longer, but there are other variables such as the mix. A high volume of latex admix will slow down the effect of the acid quite a bit for example. Pure, neat Portland can also be difficult to etch because it is so dense. Combine the two (as I often do) and you wind up with an almost acid-proof product.

I don't recommend non-professionals using full strength Muriatic Acid as it can be very hazardous to work with. You might try diluting it 20% (1 part acid to 4 parts water)and run some timed tests on some mix samples, then bump it up slowly if needed. Just exercise a great deal of respect for what you are working with. Remember..."Muriatic Acid" is simply the name given to Hydrochloric Acid that has been diluted. And Hydrochloric is very powerful stuff. Minimum safety includes splash-proof goggles, LONG acid-proof gloves and some way to avoid breathing the fumes (a fan, proper respirator, scuba gear...).

Just proceed with extreme caution. And remember to always follow the old rule..."Do like you ought'er, add acid to water". Never, never, ever pour water into acid. It can cause a spontaneous steam explosion that could really ruin your day.

If I've scared the B'Jesus out of some of you...excellent. That was the idea. Acid is very handy stuff and it CAN be worked with very safely...but only if treat it with the respect it deserves. Do a few Googles and read up before you dive in.

Scuba gear?"dive in"?You an old diver,hm?
Anyhow,thanks for the response.I've been very careful(always outdoors,never put my face over the acid,gloves on)
so far but,thanks for the reminder.And the info.I've been using 100% admix on most projects,except for my masks(about 25% admix here)and its the masks that I want to etch.So,off to the lab,and check out what's on the slab(Rocky Horror, anyone?)
Cheers from here

Rick if you decide to don your wetsuit, or even better a drysuit, while scrubbing down your Tufa be sure to post a picture.:)
Don't forget the fins.

Dont plan on ever using an acid wash but for some reason I cant get this tune outta my head.......Lets do the time warp again........lol

carey

p.s. and dont even know if were thinkin the same rocky horror lol

What does an acid wash do? Is this a way to create texture? a way to change the surface color? sounds interesting.
Laura

I used to make reconstituted stone garden ornaments, and dipped them in an acid bath afterwards. But...one thing I like about the idea of working with hypertufa is that I needn't bother with the acid bath. It really is scary stuff to work with - if you have it in a large container (like a plastic dustbin) you need some kind of cradle for lowering items into the acid. When you lift items out, acid can splash all over the place. Splashes will rot your clothes.

Then there's the problem of where to store the full-strength containers of acid, and how do you get rid of the used acid when you're finished with it? I'd really really really think it through before embarking on acid-etching!

For dumping,we've got 6 acres.Lots of spots to dump when the bath is exhausted.And,I do it as a brush on,leave it for 15 minutes,then douse with water.Haven't done the next step that others talk about namely a wash in sodium bicarbonate,but I may.I'm only doing small pieces at present.
But,hey here writes the guy,who,while in high school, decided to see what would happen if you added an alkaline solution to,you guessed it,an acid solution.WHAT a mess!And I still passed the course.
Cheers from here

Hi Dog
My bottle of acid is many years old and never opened, although I have had urges to try it.
I'm not exactly sure what acid etching does to the finish when dipped but I 'etch' with a small sand blaster (very cool), sugar applied with a paint sprayer, and good ole elbow grease with strong vinegar and wire brushes.
The only method I have fully under control at this moment is the vinegar and wire brush.:)

I have no idea what acid etching would do to a recipe made with cryogenic perlite and I hope to never find out.

What does the sugar/paint sprayer do?

Hi Dog
Spray sugar on damp concrete and it retards the surface curing. This is the bain of all leaf casters but to an exposed aggregate fan like me it is very helpful.

I use the sprayer in the link because it used canning jars.
I have a pile of these filled with paints and even admix for spraying on my half balls before applying my final coat of tufa. You just unscrew the jar and put on a lid. Then screw on your jar of cleaner to clean the gun. The paint, glue, concrete sealers, etc never touch the gun
This sprayer is terrific and I plan to add concrete stains to my stock of canning jars this winter.:)

Here is a link that might be useful: Paint sprayer to die for. Excellent for concrete.

Hey, Tufaenough,
what kind of sand blaster you usin? And what kind of sand, fine round? What effects are you getting?
Can we see a picture of the before and after, if you can post them?
Sorry for the string of Q's, just got back and got little time to spare.
BTW, I've used acid routinely for yrs, and never had a problem. Maybe a much different application.]
Thanks,
Slate

Cheap, disposable bristle brushes can be used to apply acid if you want to avoid the hazards inherent in "dipping". Also saves on acid if you aren't doing production line work.

Rick...you must've had a very "understanding" chemistry teacher who appreciated your rampant curiosity.

Tufaenough...Great looking little sprayer that begs a few questions if you don't mind. Who's the manufacturer? Will it handle heavier, more viscous materials? Are there different nozzles for different materials?

Tufaenough...never mind the info, just found it on Amazon for $39 bucks and ordered one. Thank you, this is just the type of siphon sprayer I've been looking all over for to apply my rust converter!

Hi Slate
I use the Sand Blaster in the link.
You can get one that sucks sand with a hose cheaper but I like this better.
I'm using copper slag and glass for blasting.
They are cheap and not dangerous like silica sand.
It does a great job of exposing aggregate and experiments on damp just casted concrete are pretty interesting. It can really chew the stuff up. It tears perlite and peat right out of the surface for instant age. Not much different that a wire brush look.
I have done anything really spectacular yet as I'm just getting the hang of controlling the thing. I had to get a new compressor as my old one wasn't up to the job.
I have a Moai planned to see if I can use the sand blaster to carve it like the winds do.

Here is a link that might be useful: Sand Blaster

Hi Tango
You won't be sorry.
Just plan a trip to a flea market or garage sales to stock up on canning jars.
Trust me you will need two or three dozen in no time.:)
It even does very controlled pesticide spraying.
I simply love the thing because clean up is minimal.
Have a few jars with paint thinner, soapy water, etc and it cleans itself.