How to Acid Stain
A Project Checklist & How To Guide for Applying Tru Tint Acid Stains
1. Cleaning Gear
- Mop, brush, bucket
- Wet-dry vac to suck up water and waste (maybe, depends on your specific situation)
For tough stains / dirty concrete:
- Pressure washer (works well - just be careful not to create etch patterns into the concrete with the pressure washer)
- Soap and/or degreaser (for removing oil-based materials)
- Plenty of rags or paper towels
2. Safety Equipment
- Chemical goggles
- Respirator (most building supply or hardware stores will have these)
- Fan for ventilation purposes (depending on environment/situation)
3. Application Equipment
- Plastic garden sprayer with a good dispersing tip
- Quart sprayer (for small areas or highlights)
- Acid brush
4. Materials to Protect Surrounding Environment
- Plastic sheeting
- Painters tape and/or duct tape
5. Staining Supplies
- Your selected Tru Tint Acid Stains
6. Acid Stain Neutralizing Agent
- Household ammonia diluted 10:1 with water (Ammonia : Water, 1 : 10)
- Sealer or wax (properly selected for your application and aesthetic desires)
Acid Staining Process
1. Check Weather and Site Conditions for Acid Stain
- Application temperatures should be 50ºF or greater (the higher the temperature, the quicker the reaction rate)
- A 24hr window of dry weather
- Low wind is desirable if outdoors
- Dust-free environment (ie. drywall sanding, grading the yard, etc. should not be performed in same area as acid staining)
- Access to a water hose / faucet and soap (to wash acid stain off if you come in contact, to dilute the stain, and for cleaning)
2. Do Your Prep Work for Acid Stain
Check to see if your floor has been previously sealed by applying water to the surface. If the water does not readily darken or soak into the surface, then the floor has probably has has some type of sealer on it. You can't always see sealers because some penetrate and/or leave a neutral color and sheen. A light coating can typically be removed with a red pad and a buffer. A stripper will be needed if a heavier coating is present Tru-Strip from Walttools is a biodegradable stripper that works extremely well. Occasionally, even after a stripper has been used, a mechanic scrub may be necessary. Always check the floor again after cleaning for water penetration.
You must start with a thoroughly clean surface for best results. A scrub brush, water, soap, and elbow grease will frequently do the trick. For stubborn floors you may need a pressure washer, brush, and a cleaner/ degreaser. A rust remover can be used in small quantities for areas that need it. After the floor is perfectly clean, flush with water to remove any residue from the cleaning process, vacuum or squeegee clean, and give it a final mop.
3. Gather and Set Up Protective Gear
Protect yourself! Provide adequate ventilation in the application area. If you are indoors, open windows and use fans for exhaust. Wear chemical goggles, gloves, and boots. Wear a chemical respirator (not a dust mask). Do not breath fumes from any acid stain and avoid contact with skin and eyes. Remove pets from application area. Use caution with acid stain. It is corrosive and contains metallic salts which can be toxic.
4. Testing Your Selected Tru Tint Acid Stain
Let floor dry 12 to 24hrs after cleaning. Test your stain for color, penetration, and reaction in an inconspicuous spot. Brush apply the acid stain to the substrate. Use plastic containers to hold stain, not metal containers. Let the stain fully develop color and react. This may take hours depending on the floor. Wait 24 hrs to be safe. The stain can be used as is or diluted as much as 2:1 with water. Usually dilution will lighten the color but will also make it less effective at penetrating/ etching the surface. Always test for an idea of results. Acid stain will vary even on the same slab because of cementitious content on the surface, different pours, different cement providers, finishing techniques, contaminants, temperature, application technique of the acid stain. After you are satisfied proceed to the next step.
5. Protect Walls and Surrounding Areas
Acid stain will stain or damage many items. Take caution and save yourself headaches by properly taping and plastic sheeting walls, floors, furniture, etc. - anywhere you think droplets of stain might touch, and then some.
6. Apply the Acid Stain
Apply Tru Tint Acid Stain with a plastic pump sprayer suitable for acid. Make sure the sprayer has a quality, plastic spray-tip to evenly disperse the acid stain. Apply in a consistent spray pattern, slightly overlapping. Apply the acid stain generously - enough to get complete coverage but not so much there is large puddling areas. If the floor is highly troweled or "burnished," an acid deck brush would be advisable to help the stain penetrate and react. As the acid stain is sprayed on, have a helper work it in with a short circular motion. Do not step on fresh or reacting acid stain as it can leave footprints in the final finish, if you have to scrub it back out with a brush.
7. Neutralize the Surface and Stop Reaction
You can let acid stain fully react which could be 24 hrs or stop it short. You can test the floor for reaction and penetration by wiping the residue away and there should be the true color underneath and will not rub off. The stain should be obviously adhered to the substrate. Stopping the reaction before it is complete may result in extreme variations of light to dark and possibly lighter floor in general. Neutralizing the acid stain with an alkaline substance will stop it. The most common materials used are ammonia diluted 10:1 with water or baking soda and water. Either can be applied with a sprayer generously. Household ammonia is a better choice because it does not leave a residue or have to be worked in.
8. Clean Off Residue
There will be residue left on the surface that needs to be removed to reveal the true color and allow a sealer to properly adhere. Rinse/flush surface with water and mop or shop vac as required. Give the surface one more washing with a mop and/or rags. If the final surface is exceptionally clean, the sealer adheres much better and high clarity or depth is obtained.
9. Protecting Your New Surface
The selection of your sealer is based on many factors. If the project is outdoors then an acrylic urethane, acrylic, silicone, silane acrylic, or silicone silane would be advisable. There are many of these products out there. Some work poorly and others work exceptionally well. It also depends on the substrate or whether it will have traffic etc. Through our many years of hands-on experience, advanced chemistry, and testing, we have excellent sealers for acid stained surfaces. You can find them in the products section. If you are sealing an interior floor more options are available - you can use any of the above and polyaspartic, epoxy, and urethanes.
See Sealers for more info.
A variety of advanced techniques can be employed to achieve a variety of unique finishes. See Advanced techniques
Visit our parent site www.walttools.com for all your decorative concrete needs.
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