smoothing surface after roughing
I'm planning on using an acrylic stain to cover my interior lower level. There's no drain in that area, so I've decided against using a chemical etcher, but instead am going to use a rented concrete grinder to rough up the surface.
I really want to do this RIGHT the first time. So, I have 2 questions. After roughing up the floor (I was told by a professional to get it to an 80 grit sandpaper roughness) how do you then get it smooth enough to walk on again?
And, am I correct that I DO NOT need a primer before applying the stain? Some products say you do, but again, the professional I spoke to briefly indicated I do not. I'm inclined to trust him.
Please help me clear up these questions. We're eager to start, or to call in a professional if that's the way to go.
I was told that the stain will not soak in unless I etch/rough up the surface. That it will just sit on top and eventually peel off.
what kind of stain are u applying?
my bad......ok I assume you're using a penetrating acrylic rather than membrane forming. Ok, please tell us what kind of slab we're dealing with here.
if you're going to use a water-based acrylic stain, you need to etch the floor with diluted muriatic acid. this will give you a medium grit sandpaper texture and allow the stain to adhere.
grinding the floor is not going to help. first, it will leave swirl marks. you will see them through the stain. second, it's still going to leave a smooth surface when you're done, not the medium grit texture you're after.
the top 1/4" of concrete is dense cement paste with fine aggregates. pores and microcracking are distributed evenly throughout. whether you grind down 1/32" or 1/8" the porosity is going to remain the same. grinding is not going to "open up" the surface, that is a fallacy. regardless, it's not increased porosity you're after, it's surface texture and undulation.
Thank you very much for responding and for your very helpful answer. Here are my follow up questions.
I am dealing with an interior basement w/no drainage. My understanding of chemical etching is that there's a lot of water and washing involved. I'm not sure where I'd put the water I'm washing away.
And, are there not-so-harsh etching products out there? Most seem to require full body armor. I'm concerned about that for safety and the environment.
Third, and last question, if I use an acid stain instead of the acrylic stuff (I like the look of acid better), what is the floor prep? I understand you don't use a chemical etcher when using acid stain, but what prep is needed?
All knowledge appreciated very much.
when you etch or acid stain concrete, you rinse with an ammonia-water solution (around 8:1 dilution). that means the rinse water generally has a neutral, or at least non-corrosive ph. you suck it up with a shop vac, then take it outside and pour it into the ground.
the best way to etch is with muriatic acid from a home improvement or paint store diluted about 8:1 with water. just use some protective rubber gloves and a sprinkling can and you should be all right. just don't put your face down into the solution, wear a respirator if you have one. some companies, like smith paints also have etching solutions that are non-acidic.
acid stain is muriatic acid that is diluted about 15 or 20 to 1 with water, so it is even less corrosive than your etching solution would be. to prep for acid stain, rent a rotary floor machine from home depot, attach a black pad, and use a cleaning detergent like simple green to clean the floor. then rinse. but with acid stain, as opposed to acrylic, you have to make sure you remove any paint, glue, chalk, or other contaminants that would prevent the stain from reaching and reacting with the concrete.
acid stain provides a marbling effect that acrylic stain does not. i think it looks better, but acrylic stain, well applied, looks good too. either way, you have to deal with a corrosive liquid. but again, acid stain is less corrosive than an effective etching solution.
More great info.
When rinsing the etching solution can I just pour the water/ammonia mix from a bucket onto the etched area and mop it around then suck it up? I imagine working in small sections is key here.
Is cleaning necessary before etching? Seems that would clean it all up.
I am beginning to feel like I can do this....yours is the first sensible information I've received.
use a plastic sprinkling can for etching and neutralizing. you can do about 100 sq.ft. at a time with a 2-gallon can. use a long handled scrub brush to move the neutralizing solution around. that will help keep the cement/sand residue loose so you can suck it all up.
i would clean the floor before etching. etching removes and abrades the surface of the cement but it does not provide a surfactant that will help remove dirt and contaminants. that's where you need a detergent. clean the floor, then etch it.
but if the surface is not tightly trowelled and already have a rough texture, you may not even need to etch it.
sorry my info wasnt "sensible" enough..... I was trying to see what type of concrete we were dealing with as well as ventilation issues to point u in the right direction. Good luck. Acid stains are made of hydrochloric acids by the way.
You are a home-project lifesaver. My thanks is many.
I've been trying to find the answer to the same question that afpardoe posted 4+ years ago and wondering if there is a simple answer:
I have a light pour cement floor in my entire 1-story new construction house, waiting to be finished. My cement guys gave me a nicely smoothed machine-troweled finish, knowing that I was likely going to finish it myself.
I was intending to use Smith's Green Clean before staining, which I understand both deep cleans and provides some profile, which permits an acrylic stain to "penetrate" the slab. The Green Clean leaves the cement at about a 100 grit, however -- much rougher underfoot than my lovely slab is now. If I go that route, must I then grind the slab after I stain it in order to regain the nice underfoot feel? Don't I risk losing the stain if I do that?
Would a reasonable alternative be to clean (using the auto scrubber with a black pad and rinser) with Simple Green instead? Will that severely compromise the slab's ability to take the stain? (On that score, my slab (in raw unprepped state) seems to have taken my stain samples well).
Thanks for any advice.
why are u roughing up the surface?