How to add acid stain to a concrete floor

Why would you add acid stain to concrete? What effect will it give?

Concrete is a material that is enjoying somewhat of a revival in fortunes, certainly a revival in how people are beginning to ‘see’ it. It is a material now worth its weight in gold; its versatility makes it a popular material as with the addition of chemicals and other treatments, it can be used to create a variety of different, appealing finishes.

But, it is not a do-it-yourself job for over the weekend… it is a task that takes knowledge and skills and, in most cases, should be left to the experts. There are many skilled companies that offer such services, such as the highly reputable Midland Polished Concrete company.

An ‘acid stain’ – what does it produce?


The addition of an acid stain to a concrete floor creates the most wonderful of marbling effect, a sense of drama into a room as well as being visually appealing. In terms of colour, it has a depth and richness that you will be hard pushed to find in any other kind of flooring material. And, in only a few small steps, a professional company can create the marbling effect you desire, in the colour you want…

Step 1: Preparation

When adding acid stain to a concrete floor already laid, the walls and any other low-lying fixed objects will need to be protected from the discolouration process of the acid stain. You may find that this takes time as it is imperative that this is done to a high standard, with attention to detail.

Step 2: the acid stain mix

Acid stain is a chemical treatment process with many ingredients, the most active one being hydrochloric acid. A form of this acid is found in the intestinal tract and is used by the body to break down food and drink; as a manufactured chemical substance, it has a variety of uses, from altering the compound structure of some materials to make others and for use in heavy industry. In a much more diluted form, it is also used in the purification of water, as well as in pharmaceuticals and food.

In the case of acid staining of concrete, it is far more concentrated than this, and thus need carefully handling which is why it is best left to the trained professionals. Safety equipment will need to be worn, as well as the chemical being mixed and used in a well-ventilated area.

The equipment used to apply the treatment must also be plastic only, as anything metal will be corroded by this highly concentrated substance. Likewise, the mix of the hydrochloric acid to water also needs to be correct in order that the right result is achieved.

Step 3: application

How the substance is applied to the floor is important, as this will give the lasting dramatic marbled pattern that you want.

The floor needs to be thoroughly wet by the hydrochloric acid substance, but with no pooling. The acid in the spray reacts with the limestone in the cement component of concrete. This reaction creates a myriad of colourful hues, creating the marbling affect that so many people find attractive.

Each coat of hydrochloric acid needs to dry thoroughly, with each coat after this creating a different shade and colour. You need to be aware that this is an organic process, and uniform results across the floor cannot be guaranteed. This is because there will be concentrated ‘pools’ of limestone deposits in certain areas of the floor, and these areas will react more readily with the acid, creating darker areas.

Step 4: setting the result

Once the desired result has been reached, the results now need to be set so that the result stays looking fabulous!

This is a two part process:

  • The stain needs to be neutralised and this is done using a water and ammonia mix; again, ensuring that you have the correct combination can be difficult, therefore rely on a professional company to complete the whole process guarantees a far more reliable outcome.
  • Once this has been done, the floor will need mopping with any excess water ‘vacuumed’ with a wet vacuum cleaner. The floor needs to be thoroughly clean and dry before the next stage.

Step 5: sealing

Sealing has a two pronged benefit:

  • It seals the floor against every day wear and tear
  • It highlights and enhances the marbled effect in the concrete floor!

Polished concrete floors are all sealed for this reason; even concrete used outdoors, such as on driveways are also stained to help them fight the ravaging effects of weather.

Again, a professional company will be able to deal with the whole sealing process quickly and easily, without compromising on the finish. Two coats usually suffice to bring out the best in the colours.

All that remains is to remove the protective borders and enjoy your new-look marble effect concrete floor!

For the more visually inclined of you we have created the below infographic.