How To Remove Acid Stain From Concrete

Acid staining can be a bit tricky when trying to achieve a certain color. When you are not happy with the color of the concrete floor after acid staining, the only practical way to remove an acid stain from concrete is by using a grinder to mechanically remove the top surface of the concrete where the acid stain is. After grinding the acid stain off, we recommend using a dye to re-stain the concrete floor.

Before Removing Acid Stain From Concrete

Before Removing Acid Stain From Concrete

 

After Grinding The Acid Stain Off

After Grinding The Acid Stain Off

 

 

 

How To Clean Concrete Before Acid Staining

Cleaning concrete before acid staining is the most important step. You want to make sure there is nothing on the concrete that will prevent the acid stain from soaking in the concrete.

There are a few tools that you can use to help clean the concrete:

  • Scrappers 
  • Floor Machine
  • Shop Vac
  • Scrubbing Pads
  • Detergent (nothing that contains acid)
  • Mop
  • Mop Bucket
  • Xylene

The first thing we do when we clean concrete, is run the floor machine with detergent (typically dawn soap) over the whole surface to remove dry wall mud and any loose paint. This will help you see what is left on the concrete that needs to be removed.

If there is glue that is still on the floor, you might need to use a solvent such as xylene (make sure pilot flames are blown out) to remove it. If there is paint still on the floor, scrape as much of it of as you can, then go over the surface with xylene to remove any stubborn areas. If the whole surface of the concrete floor is painted, you will need to use a chemical stripper or grind the concrete. If you grind the concrete you will have to grind the whole area to make sure the surface texture is all the same. If the paint and glue remain on the concrete floor when acid staining, you will notice them.

After you have removed all the contaminants from the floor, use a mop with clean water to thoroughly clean the floor. Let the concrete completely dry out and then you are ready to acid stain the concrete.

The Process Of Scoring & Acid Staining Concrete

The other day I was called to look at a patio a DIY’er scored and acid stained. He was having problems with the lighter acid stain color making stain marks over the black stained border. I have never seen a lighter acid stain taking over a darker acid stain color, but after seeing this patio I now know it is possible for a lighter stain color taking over a darker stain color.

The process he used to score and stain his patio was: he first scored a border around the patio; he then sponged on a black acid stain on the border; after the stain had dried, he taped off the border and stained the middle of the patio with a lighter acid stain which bled under the tape and made rusty color stain marks over the black.

The most common way when scoring a decorative border around the patio and acid staining is to: first score the border; then stain the whole patio with the lighter stain; and then after the stain has dried, paint on the black or darker colored stain around the border. When doing it this way you will not have to worry about taping off the border and the stain bleeding under.

Staining Old Concrete Floors – Can It Be Done?

Staining old concrete floors can be done with the right knowledge about the concrete floor and with hard work prepping the concrete. We have stained an old concrete floor that was poured in the 1920’s and the floor came out amazing.

If you are planning on acid staining an old concrete floor that has been poured a long time ago, the first thing that should be done is to test the concretes porosity. Sprinkle a few drops of water and check to see if the water is soaking into the concrete (the concrete will appear darker and the water wont beed).

If the water soaks into the concrete, the next step would be to see if the concrete will accept an acid stain. In an area that wont be visible apply a small amount of the acid stain to the concrete and wait a few hours. If the concrete is not changing colors or the color is very faint, the concrete might be lacking the necessary lime for an acid stain to work. The next best thing to stain concrete, with out worrying about the lime content in the concrete is an acetone dye or water based stain.

The only main thing you have to worry about when using an acetone dye or water based stain when staining an old concrete floor is that the concrete is able to soak the dye in and that the concrete is free from any paint, oil, glue, or any thing else that might prohibit the penetration of the dye. These stains will give a look vary similar to an acid stain.

 

 

Acid Staining A Concrete Wall

Acid stain and concrete dyes can be used to stain a concrete wall. When staining a concrete wall you want to make sure the concrete is clean by pressure washing and using a mild detergent to remove anything that will prohibit the penetration of the concrete stain. Once you let the concrete wall dry you will start by spraying the bottom of the wall with the concrete stain and work your way up to the top of the wall. After you are done staining the concrete you will want to seal it to help keep it clean and protect it from the sun.

Some type of walls that may be stained:

  • cinderblock walls
  • stucco walls
  • regular concrete walls
  • rock walls if using an acetone dye
  • exterior sides of foundation

Staining a concrete wall is a great and easy way to add color to the wall with out using expensive materials.

Resurfacing Old Concrete

There isn’t just the option of tearing out and replacing old worn down concrete. You have the option to use a modified-polymer cement to resurface the concrete, just as long as the concrete is structurally suitable.

Typical concrete resurfacing applications are used for restoring concrete that has been eroded, coated with a paint that is peeling off, concrete with a bad surface finish, concrete with shrinkage cracks, and spalled concrete. After the concrete has been resurfaced it can then be either sealed the way it is or the concrete can be stained using an acid stain or dye.

The proper steps for resurfacing concrete to insure a good bond are:

  • Grind concrete to produce a profile
  • Resurface concrete with a rough coat
  • Resurface concrete with a smooth coat or rough coat for a second time
  • After resurfacing cement has dried sand area smooth
  • Acid stain or dye the resurfacing cement
  • Seal resurfacing cement

Concrete resurfacing can be done inside and outside and the product we use is very durable for heavy traffic applications such as retail stores and parking garages. It can be applied with ether a smooth finish, skipped troweled finish, or a sand finish for exterior applications.

 

concrete resurfacing

Pitted concrete is being resurfaced before acid staining.

Concrete Staining Tip – How To Spray Acid Stain

When it comes time to acid stain the concrete, the best way to apply the stain is by using an acid resistant pump sprayer. Make sure all of the fittings are tightly secured so there wont be any leaks.

It is always good to have someone with you when acid staining the concrete; they will assist you by holding a bucket close by incase the sprayer starts leaking you can place the sprayer in the bucket. It is also good to start spraying inside the bucket then remove the sprayer tip when you see a nice mist coming out of the nozzle.

When you have to stop spraying you need to stop inside the bucket or else the nozzle will drip big droplets of acid stain onto the concrete permanently staining the concrete. This happens because  once you let go of the trigger the pressure in the tip will decrease and any acid stain in the tip will just drip out instead of spraying out. If you do notice a drip on the concrete try to spray a little more acid stain in that area to minimize the look of the round dot that will be stained on the concrete.