Colour Concrete / Acid staining
Acid stain can be applied to new, old, plain concrete or overlays. Overlays are required to coordinate with colour consistencies. Although they are often called acid stains, acid isn't the ingredient that Colour's the concrete. Metallic salts within acid, water-based solution reacts with hydrated lime (calcium hydroxide), Colour's compounds that become a permanent part of the concrete. Once the acid reacts it remains a permeate stain.
There are 8 Colour's that form the foundation. The acid in chemical stains opens the top surface of the concrete, allowing metallic salts to reach the free lime deposits. Water from the stain solution then fuels the reaction, usually for about 12 hours. The acid is then removed by specialty products and flushed thoroughly to seize any further reactions.
Some important facts of acid staining
- No two independent floors are identical.
- Every stain reaction varies! Used aged concrete (could require an overlay)
- Moisture content within a slab when staining may cause efflorescence to appear, also alters finish product.
- Cements that produce a larger amount of calcium hydroxide during hydration will intensify stain colour, and higher cement contents pro-produces more intense colours.
- Air-entraining or water-reducing admixtures don't pose a problem. However, calcium-chloride accelerators can cause very mottled, darkened areas, and for this reason aren't recommended.
- Open finishes achieved by floating followed by minimal trowel-ling take more stain and produce denser colours than do hard-trowelled surfaces. However, open finishes lose colour faster because the concrete wears away. We recommend staining on hard trowel- led surfaces, because the stain colour lasts longer. "Colour's on trowel-led surfaces also look richer than those on floated surfaces”.
- If the surface needs to be sanded, we recommend applying an underlay to compensate the low hydrated lime. Slabs placed in wet weather result in a richer stain colour if the concrete is stained soon after it's placed. However, wet slabs are more likely to effloresce, lightening the colour and causing a more blotchy effect in areas where the stain doesn't take due to efflorescing salts hindering penetration.
- On sunny days, the concrete can become hot and dry, and the stains won't penetrate as deeply into the concrete. The continued presence of water will cause the reaction to continue for a long time, and concrete stained blue-green will gradually turn brown or even black. Initially, this provides nice variation to the appearance, but eventually, nearly all the blue-green colour may change to brown and black. For this reason of the possible colour shifts, some manufacturers advise against using these Colour's for exterior concrete. Interior slabs must be placed on a well-drained base or sub-grade and have a low moisture content before stain is applied. Winter seasons are not suitable for acid staining