guide:

Coloring Plaster with Limewash

A LIMEWASH COLOR FINISH is a mineral-based paint formulated for easy application and simple repair and touch up. Limewash creates a thin calcified mineral coating with a subtle matte finish with a soft and porous feel. Limewash is not a film-forming coating, and does not contain synthetic binders. Rather, it is absorbed into the plaster and becomes part of the render, forming an integral bond that will not flake or peel. Limewash is best suited for light-to-medium colored finishes.

open and absorbent

For a limewash to bind properly with a lime plaster finish, the surface must be OPEN, meaning that it must have some porosity and texture. Technically, it comes back to absorbency: a highly polished, tight-finished surface has been “closed” to the point that it is not really absorbent enough to accept and hold a limewash. To successfully color tight, polished plaster finishes, the colorant/pigment must be added to the finish coat mud itself during the mixing.

COVERAGE. Coverage rates will vary depending on the texture and openness (tightness of finish) of the surface to which it is applied. A good rule of thumb is 100 square feet per gallon at two (2) coats.

PREPARATION. Application of limewash can be a sloppy process. Take appropriate measures with masking and protection to ensure you don’t damage/discolor adjacent surfaces. Limewash will stain unfinished wood and porous floor coverings.

mixing limewash

STEP 1. Add the full amount of water to a clean bucket. Water amount is calculated at 3.3 x the dry lime powder when measured by gram weight [1].

FOR EXAMPLE:
• 2 lbs / 907g limewash powder X 3.3 = 2993mL [3 liters / 0.8 gallons] (1 milliliter volume equals 1 gram weight);
• 10 lbs / 4536g limewash powder X 3.3 = 14,969mL [15 liters / 4 gallons]

STEP 2. Using a mixing drill and paddle, gently stir the pigment or colorant into the mix water (see pigmenting). Some pigments will take more time to fully hydrate. Once all of the pigment is hydrated, mix vigorously for 1 minute.

STEP 3. Add the limewash powder to the water while stirring with the mixing drill. For best results, add the limewash incrementally, not all at the same time. Once all of the limewash has been added, mix vigorously for 1 to 2 minutes. The mixed limewash should be the consistency of whole milk.

Mixed limewash has a high solids content; the pigment and lime will settle quickly to the bottom of the bucket. When working with limewash, it is IMPERATIVE that you continue to stir by hand every few minutes.

Once mixed, the limewash keeps forever, as long as is not allowed to freeze or evaporate. Store tightly covered in a temperature-stable environment.

OPTIONAL STEP. Pass the mixed limewash through a bag-type paint strainer. This will sieve out any hardened particles of pigment or lime that have not fully incorporated.

[1] • See water and color pigment CALCULATORS to figure amount ratios.

pigmenting

Limewashes can be pigmented with dry powder pigments or universal paint tints. We recommend our LSB Color System pigments, as they have been selected to work well with our Limewash.

It is highly recommended NOT to exceed 100 grams of pigment per gallon formula of limewash (multiplier 0.11). Too much pigment can overwhelm the lime binder and cause dusting and durability problems. Because of this limitation, it can be difficult to achieve dark colors with limewash. Think of limewash as a light-to-medium colored finish.

dampening

The plaster surface should be lightly misted before limewash application. If limewash is applied without first misting the surface, it can dry out too fast and inhibit curing. When dampening the wall, the water should absorb quickly into the substrate and not remain wet/beaded on the surface. Ambient conditions will effect this and common sense should be applied.

application

Limewash is best applied using a big brush with absorbent bristles. Look for a “block brush” or a “stain brush;” these are large (up to 8 inch) brushes with natural bristles that can absorb limewash. Do NOT apply limewash with a roller, as there is a good chance you will leave lap lines and roller marks. Spraying limewash is also NOT recommended—because of the high solids content and tendency to settle, limewash will likely clog spray equipment.

You should also have some type of stir stick that stays in the bucket as you are working with limewash. That stick will remind you to constantly stir the limewash while you are working with it.

Using the proper brush, apply the freshly-stirred limewash in a consistent pattern, scrubbing the limewash into the texture of the wall with the brush. Common techniques are vertical, horizontal, crosshatch and figure-eight. Avoid creating drips and runs. Wash the whole wall at one time and maintain a wet edge. Do not apply limewash in freezing weather, excessively hot or windy weather, or to surfaces that are saturated from environmental conditions.

TWO COATS. Limewash should be applied in at least two coats. There is no maximum number of coats that can be applied—the look and color depth you’re going for dictates how many coats will be needed.

WORK IT OUT. Limewash, when freshly applied and in a wet state, can appear somewhat translucent. It is very tempting to apply too much. Keep this in mind: you are creating a thin layer of calcification that is integral to the surface, not trying to build a film like with ordinary paints. First work out the color depth and application pattern you want on cured plaster practice panels finished with the same texture and look of the final wall finish. Limewash can be further diluted with water to create a glazed, subtle, multi-colored effect.

CURING. Allow the first coat (and all subsequent coats) to cure for a minimum of 12 hours. Mist again and apply the second coat in the same way. After curing, you can continue to apply subsequent coats to achieve the effect you desire.

OPTIONAL STEP. Because our limewash does not contain acrylic binders, there is a chance of some slight dusting when rubbed, depending on the curing conditions and number of coats. To resolve this, wait at least 24 hours for the final coat of limewash to cure. Then take a soft cotton rag or old clean tee shirt and buff the walls. This will remove any areas that are dusting and—depending on the texture of the substrate—can give the limewash a smooth patina.

clean up

The best way to clean limewash from surfaces it does not belong is to let it dry, then use a soft abrasive material to “sand” it off. If you clean it after it cures, it should turn to powder and come right off. If there is residue left behind, use plain white vinegar as a solvent to remove it. /p>

safe use precautions

Limewash contains hydrated (slaked) lime, which (because of a high pH) is somewhat caustic. Breathing the powder dust can also cause respiratory irritation. BE SMART. Protect yourself. In all situations, if irritation develops, seek medical attention. Please read our Safe Use Precautions and Treatments publication for information on protecting and treating skin, eyes, and breathing function.