How to know when etching is complete?

[mfive]

Gang, I'm in the middle of etching the floor and I've seen in previous posts that it should feel like 120 grit sandpaper afterwards.

There's no way this is getting down to that type of etch. It's fizzing and bubbling and in some areas turning yellow (too strong?), but after it's done bubbling I'm rinsing it off only to find that the concrete doesn't look or feel much different than before.

Is that normal?

 

[OBP]

Mfive, don't make the mix too strong, about 1 part acid to 4 parts water is good, it should fizz like your getting, keep in on there for about 10 - 15 mins, lightly spray water around to keep it wet not water it down.
I agree etching never will get the cement down to a 120 grit finish, the best check its when your hosing off the acid make sure there are no oily areas.
When the floor is dry sprinkle a couple of drops of water on the cement, it should be absorbed quickly and dry out quick too.
I hope that helps.

 

[Edger]

mfive, completely agree with everything OBM says, that last test is what matters.

 

[Rich H.]

Good deal, I needed to know this also.

 

[csp]

You really need to go over the surface with a stiff broom/brush to dislodge the surface concrete that the etch loosens up. Pressure washing also helps.

Just rinsing the etch off isn't going to do anything.

 

[munkey]

I had the same problem... etched over and over with varying strengths and still never got the surface feeling anywhere close to 120 grit. It seems that the amount of roughness you'll end up with depends more on the exact type of concrete you have than anything else.

The one constant with acid is that it is very important to pressure wash the surface afterwards to get the white cement powder out of the nooks and crannies that the acid will produce; you really don't want to apply your coating to a layer of dust sitting atop the actual surface. Believe me when I say that a regular hose/nozzle is NOT sufficient to remove this dust; the frustrating part, if you want to try it, is that you won't be able to tell that it failed until all the water has dried up and there's still a white haze to the surface... and you've lost valuable hours. (The same problem happens if you pressure wash and miss a few spots: when the surface is wet, it will look good, but when it dries you'll be able to see the spray pattern you used and areas that you might not have paid enough attention to.)

 

[Falcon67]

Well, FWIW - the last old shop was etched with a 50/50 mix of pool acid and water. Mopped on, let set a bit, then rinsed with a hose. I then mopped it with a diluted baking soda/water mix. Rinsed again, swept with a nylon bristle push broom and dried. Epoxy paint and moved in after 48 hours. I don't remember if there was any haze on the floor. Once it was dry, on when the epoxy. It was not very rough from what I remember.

 

[mfive]

You really need to go over the surface with a stiff broom/brush to dislodge the surface concrete that the etch loosens up. Pressure washing also helps.

Just rinsing the etch off isn't going to do anything.

What a world of difference the pressure washer made!

Although, it did **** taking a 2-inch spread of water across my entire garage floor. I did miss a couple of spots and tried to go over them again with a brush and water, as after they get wet it's impossible to see. Did anyone else have very slight lines where you could see in certain areas where it was lighter than others from the pressure washer not being 100% consistent?

Should I pressure wash it again!? The only downfall is you can't see which parts are missed once any water gets on the floor...

 

[mfive]

Mfive, don't make the mix too strong, about 1 part acid to 4 parts water is good, it should fizz like your getting, keep in on there for about 10 - 15 mins, lightly spray water around to keep it wet not water it down.
I agree etching never will get the cement down to a 120 grit finish, the best check its when your hosing off the acid make sure there are no oily areas.
When the floor is dry sprinkle a couple of drops of water on the cement, it should be absorbed quickly and dry out quick too.
I hope that helps.

Alright, so I guess I'm not sure how quick "quick" should be... so I made a little movie.

Check out this link and see if this looks sufficient. It soaks in and spreads, but does it look "fast" enough? Apologize in advance for the not-so-steady hand.

 

[Edger]

That movie is fantastic!!! Wow, it sure is beautifully porous. In regard to pressure washing, here is a copy from another post I made today.

"I acid etched many large factory floors and went over with a power washer rotary head (like a lawnmower) which had very powerful jets and pump up to 8000psi.

I found anything above 3,000 psi removes the residue completely, but you must have the jets close to the floor. For that work we used to run it at about 4,000 psi.

I know that does not help you without the equipment, but it gives you an idea of what pressure washer power you need.

By the way, sometimes we moved the floor head across the floor too quickly and left white rings which we could not see until it dried when it was too late so we applied epoxy over them anyway. No adhesion problems occurred. That is not a guarantee though."

Your soaking of the water is plenty fast enough.

 

[OBP]

Technology is pretty cool. Yep that looks good, its not beading up on the concrete and you can see it changes the color of the concrete quickly meaning the concretes opened up pretty good ready for a coat, so from what I can tell looks like its good to go.
Please tell me after your efforts your not going to put any cheap trashy "epoxy" on the floor?

 

[munkey]

Did anyone else have very slight lines where you could see in certain areas where it was lighter than others from the pressure washer not being 100% consistent?

Yes.

Should I pressure wash it again!?

No.

I mean, you can spend days trying to etch concrete "perfectly" (which is probably why many of the pros here will tell you just to grind it -- more consistently excellent results.) The reality is you have to call it quits at some point, and judging from the video, you are in great shape. I'd bet money you get a great bond with your epoxy.

The only downfall is you can't see which parts are missed once any water gets on the floor...

Is there an echo in here?

 

[Rich H.]

Thanks to the OP for the movie and for asking basically the same question I asked, but doing a much better job of it

My slab is the same way, seems like we're both good to go

 

[mfive]

Technology is pretty cool. Yep that looks good, its not beading up on the concrete and you can see it changes the color of the concrete quickly meaning the concretes opened up pretty good ready for a coat, so from what I can tell looks like its good to go.
Please tell me after your efforts your not going to put any cheap trashy "epoxy" on the floor?

I got whatever the name of that stuff is at Lowes Depot...


Only kidding - I've been bridging the fine gap between overpreparation and paranoia because I bought the Epoxy-Coat Full Kit and I want to make sure I do a perfect job. This is my first home, and first garage all to myself and I can't wait to have this thing finished.

@Rich - glad you are experiencing the same thing. When are you coating? How's the weather there? See the attachment for my weather (I'm planning on filling the cracks with legacy industrial hD-821 Friday, base coat Saturday afternoon, and sunday morning clear coat. I'm debating picking up a space heater since my garage is uninsulated (but attached to the house). Three sides of the garage are outside walls so although it gets cooler in there, I don't think it's dipped below 50 yet, although by putting meat thermometer just setting on the ground I do see the air temp getting down very close to 50. Too close for comfort. I'm thinking of mounting an electric space heater to the wall for the weekend application.

@munkey - thanks for calming my nerves. Even more excited now!

 

[mfive]

... almost forgot!

 

[Rich H.]

It's looking like Saturday afternoon for me too, most likely.

Weather is odd, which is normal for lower MI this time of year. Yesterday it got as warm as 60, I was comfortable outside in a T shirt...but it's going into the 20s late tonight and will be 40-something during the day.

After that it's supposed to bounce right back and stay somewhere in the 50s for F/S/S so should be good to go. Best of luck with yours!!!

 

[czimmer1]

I was in the same boat on the etching. I just kept cleaning and cleaning. I have 1600 SQFT that I am playing with in my garage trying to figure out the best way to etch. I came to the conclusion that I used too much water to begin with and got minimal fizzing. I had a brand new power troweled floor and by the time I was done it wasnt smooth anymore. I am just finishing up the RockSolid floor hopefully tonight.