Internegative guide wanted

[Aurore]

Well, I called my mother, and she said it was indeed sulfuric acid that we needed for the cement, but just to be sure, I looked up 'pool acid' online.

"IDENTIFICATION OF PRODUCT
Product Name: POOL ACID
Common Chemical Names: 40% Sulfuric Acid Solution, Pool Acid
Chemical Names of Ingredients: Sulfuric Acid, Water
Chemical Family: Inorganic Acid Compound
CAS Registry Number: 7681-52-9
Empirical Formula: H2SO4
Molecular Weight: 98.0"

I got that from a 'material safety data sheet' pdf posted on a pool products manafacturers website.

But I'm glad I checked.

[clay]

Yep, that is exactly the same stuff as battery acid. It is all serious stuff. Wear eye protection and gloves when you are messing around with it.

[glbeas]

"swimming pool acid is the same thing. You can get it at any swimming pool supply place. They sell it by the gallon, and often in a two gallon pack."

You know, that's what I thought. I'm helping my mother get ready to sell her house, and the last owners turned the carport into a lanai... unfortunately, the carport cement had been painted green, so now the walkway and driveway are bare cement, but one strip of the walkway is partially green with old paint. I was pretty sure sulphuric acid was what we needed to etch the cement with... guess I can split the cost with her. Cool.

As far as battery acid, well, I think I'd rather buy the pool stuff. Must be psychological... same stuff, but somehow pool acid sounds safer than battery acid... :roll:

It may well be safer to rent a 5000 psi pressure sprayer and simply blast the paint away. Be careful though, I've seen one cut a hole in asphalt so don't point the sprayer at anything that don't need spraying. Especially at people. Going over all the concrete will make everything look more consistent.

[Aggie]

..

[Aurore]

"It may well be safer to rent a 5000 psi pressure sprayer and simply blast the paint away. Be careful though, I've seen one cut a hole in asphalt so don't point the sprayer at anything that don't need spraying. Especially at people. Going over all the concrete will make everything look more consistent."

Already done it! That's why I said 'partly' green... some of the paint came up, but not all. We did it with the 1 degree nozzle, not sure of the psi. It was a rental from Home Depot.

Thanks for all the info. I will talk to somebody at the store when I buy and will certainly be careful. The potassium dichromate is probably pretty much the same when it comes to safety, and I have the neccessary gloves, safety glasses, and respirator. Should be fun :roll:

[glbeas]

"It may well be safer to rent a 5000 psi pressure sprayer and simply blast the paint away. Be careful though, I've seen one cut a hole in asphalt so don't point the sprayer at anything that don't need spraying. Especially at people. Going over all the concrete will make everything look more consistent."

Already done it! That's why I said 'partly' green... some of the paint came up, but not all. We did it with the 1 degree nozzle, not sure of the psi. It was a rental from Home Depot.

Thanks for all the info. I will talk to somebody at the store when I buy and will certainly be careful. The potassium dichromate is probably pretty much the same when it comes to safety, and I have the neccessary gloves, safety glasses, and respirator. Should be fun :roll:

It was probably quite a bit less psi. The 5000 psi machines can darn near take the paint off a car. After the acid soak don't just turn the hose on it to wash it off, that'll splash the acid all over. Mist it down or use a neutralizing chemical before hitting it hard. Good luck!

[Aggie]

..

[Aurore]

Well, since we're on the topic anyhow, think it'll get the rest of the paint off? The suggestion from the Home Depot employee was to re-paint... the etching was suggested as a 'primer' before repainting. But I was kind of hoping it would just take the horrible paint off. I stand to benefit... this is something I sometimes do for a living (when certain friends need the help), and she will certainly be paying me once the house is sold!

[glbeas]

Wouldn't hurt to try it. If it doesn't work you can rent a sandblaster to take the rest of the paint off. While you're at it you can sandblast some glass for a light table or two for the darkroom.

[fhovie]

Funny thing about chemicals - i know that pool acid i used in the past was an imprecise blended hydrochloric -. I also know that battery acid i used as a mechanic was a clean sulfuric - for use in distilled water. I would not make any assumptions. I did find out that the soda ash I was buying for my pool was anhydrous 100% sodium carbonate, that stuff I am using in photo chemistry - I did hunt down the MSDS on the BRAND of chemical I was using to find out though.