Zero VOC
Zero-VOC paint
The VOC figure printed on a can of paint is measured on the untinted base. Colour goes in afterwards, at the factory or at the store counter, and the tint brings its own content with it. Nobody is required to retest the can after it has been tinted, and nobody does.
That is not a scandal. It is a labelling gap, and most of the industry has quietly improved its colorants in the last decade. But it means “zero VOC” on a tinted can tells you about a liquid that no longer exists.
We sell limewash, so we have an interest here. We would still rather you understood the claim than believed ours.
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Three things “zero VOC” does not mean
It does not mean zero
In practice “zero VOC” is a marketing use of a regulatory threshold, not an absolute. A product can sit under the line and still be releasing something into your room.
It does not mean non-toxic
VOC is a category defined around compounds that evaporate readily and contribute to ground-level ozone. It was written for smog, not for your lungs. Some compounds are chemically volatile but exempt from the definition, so they leave the can without counting toward the number.
Meanwhile plenty of things in a paint can are not VOCs at all and are in there for a reason — biocides, for one. A low number is good news. It is not a full ingredient list.
It does not mean odourless, and odour does not mean safe
The compounds most worth avoiding are frequently the ones you cannot smell. Using your nose as the instrument gets this backwards in both directions.
Why limewash is a different kind of claim
A reduced-VOC acrylic is a conventional paint that has had things taken out of it. That is genuine progress and it is also a reformulation — the product started somewhere else and was improved toward a threshold.
Limewash never had a solvent in it to remove. It is zero VOC by composition, not by reformulation. There is no resin, because the binder is lime itself. There is no solvent, because the carrier is water. There is no biocide, because almost nothing grows at pH 12.
And it does not dry so much as set. Lime cures by carbonation: it reabsorbs carbon dioxide from the air and converts back into calcium carbonate — limestone — on the face of your wall. A cured limewash wall is mineral. There is nothing in it left to leave.
What is in the bucket
Limestone burned, then slaked in water and aged. The binder. It cures by reabsorbing carbon dioxide from the air and turning back into limestone on the wall.
The carrier. It leaves. That is the whole of the drying process.
Ground earth and oxide pigments — the same class of colour used on plaster for several thousand years. Lime-fast, light-fast, and inorganic.
What is not
- No acrylic, vinyl or alkyd resin
- No solvents or co-solvents
- No glycols or glycol ethers
- No added biocide or fungicide
- No ammonia
- No formaldehyde-releasing preservative
Breathability, and the part that actually matters
The VOC question gets the attention, and for a wall finish it is arguably the second most important property.
A conventional paint film is a thin plastic skin. It is vapour-closed, so moisture that reaches the wall from either side has nowhere to go and sits behind the film. Trapped moisture is the precondition for mould, and mould is a larger indoor air problem than a cured paint film.
Limewash is vapour-open. It does not form a film; it keys into the surface and lets water vapour pass through. Masonry was designed to absorb water and release it, and lime lets it keep doing that.
We are deliberately not going further than this. Indoor air quality has many inputs, your walls are one of them, and anybody selling you a wall finish as a health intervention is overreaching.
Where limewash is the wrong answer
Three places, and we would rather say so than sell you a pail you resent.
Showers and wet rooms. Direct, repeated water contact is past what limewash does. That is tadelakt — a different lime system, burnished and soap-sealed, genuinely waterproof.
Cabinet doors, trim, and anything scrubbed weekly. You want a hard waterborne enamel. Several are available at very low VOC content. Use one.
Painted drywall with no preparation. Limewash bonds mechanically and cured latex is not porous, so there is nothing to key into. It needs a mineral primer or a skim coat first. This is the single most common cause of a failed DIY limewash job.
And one safety note, since nobody else prints it
Wet lime is caustic — around pH 12. It will dry and irritate skin and it can do real damage to an eye. Gloves and eye protection, every time, and rinse splashes off straight away.
That alkalinity is the same property that means no biocide is needed in the bucket. It is a feature of the material and a hazard while you are holding it.
Buy it, or have it done
The same limewash we put on client walls, custom-tinted by hand and shipped anywhere in the United States. $50 a gallon, $225 for the five-gallon pail — $45 a gallon — with the full application course included.
If you are in Dallas–Fort Worth, Central Texas or Palm Beach and would rather not learn on your own living room, we apply it. The Zero VOC Home Program moves every painted surface in the house over to lime, measured before and after.
Common questions
What is the best zero-VOC paint?
It depends on what the wall has to survive. For a kitchen cabinet door that gets scrubbed weekly, a zero-VOC waterborne enamel is the right tool and limewash is not. For walls and ceilings, limewash and other mineral finishes are the only category that is zero-VOC by composition rather than by reformulation — there is no solvent in them to have removed, because there was never one. That is a different and more durable kind of claim than a reduced-VOC acrylic.
Is zero-VOC paint really zero VOC?
The number on the label is measured on the untinted base. Colour is added afterwards — at the factory or at the store counter — and the tint carries its own content. Many manufacturers now offer genuinely low- or zero-VOC colorant lines, so this is not a conspiracy; it is a labelling gap. The honest reading of "zero VOC" on a tinted can of paint is that the base met a threshold before the colour went in. Nobody is obliged to retest after tinting and nobody does.
Does zero VOC mean non-toxic?
No, and the two get conflated constantly. VOC is a regulatory category defined around compounds that evaporate at room temperature and contribute to ground-level ozone. Some compounds are chemically volatile but exempt from the VOC definition, so they do not count toward the number while still leaving the can. And plenty of things that are not VOCs — biocides, for instance — are in a paint can for a reason. "Zero VOC" is a specific, narrow, useful claim. It is not a synonym for "nothing in it".
What is actually in limewash?
Three things. Slaked high-calcium lime putty, water, and mineral pigment if it is coloured. That is the entire formula, and it is the formula because it has not needed changing. It cures by carbonation — reabsorbing carbon dioxide from the air and reverting to calcium carbonate, which is limestone — so the finished wall is mineral rather than plastic.
Is limewash safe to use indoors?
Once cured, yes — there is nothing in a cured lime surface to off-gas. While you are applying it, treat it with respect: wet lime is strongly alkaline, around pH 12, and it will irritate skin and seriously hurt your eyes. Gloves and eye protection, and keep it off your forearms. The alkalinity is also why lime needs no added biocide, because very little grows at that pH.
Is limewash better for indoor air quality than paint?
It contributes nothing to indoor VOC levels, which a conventional paint film does for a period after application. It is also vapour-open rather than film-forming, so moisture moves through the wall instead of being trapped behind a skin — which matters because trapped moisture is what mould needs. We are careful not to go further than that. Indoor air quality has many inputs and your walls are one of them.
Does zero-VOC paint still smell?
Conventional reduced-VOC paints generally smell much less, not nothing, and the smell is not a reliable guide to what is in the air — some of the compounds you would most like to avoid have no odour. Limewash smells faintly of wet stone while it is going on and of nothing once it has cured.
Can I use limewash on everything?
No. Walls and ceilings, masonry, brick, stucco, lime and cement render, and properly primed drywall — yes. Shower surrounds want tadelakt, which is a different lime system and genuinely waterproof. Kitchen cabinet doors and trim that gets scrubbed want a hard enamel. We sell limewash and we still think you should use the right thing in each room.
How much does zero-VOC limewash cost?
$50 a gallon, or $225 for a five-gallon pail — $45 a gallon. Shipped anywhere in the United States, tinted by hand, with the application course included. One gallon covers roughly 140 square feet at the two coats most walls want, so a typical bedroom runs about two gallons.
Start with a sample
Three ingredients, twelve colours, and a real hand-brushed sheet you can stick on your own wall before you commit to a gallon. $6 a sample, credited toward your first order.
Keep reading
Who we are
Thirty seconds, then stay for the podcast.
I’m Ben Lynch. I started LimeWash Pros after reading what the EPA had published about the air inside ordinary American houses — and realizing the walls were the problem.
Meet LimeWash Pros
Who we are, what lime does that paint cannot, and why the air inside your house is the reason we do this.
The podcast
11:33From Setback to Limewash Success: Meet Ben Lynch
Why I walked away from conventional paint, what I found in the research on VOCs, and how that turned into LimeWash Pros.
12:10How Modern Paint is Killing You
The VOCs in ordinary latex paint don’t stop off-gassing when the wall dries. What that does to the air in your house.
9:43The Carcinogen On Your Walls
Benzene is a known human carcinogen and it is in the paint on every surface of your home. What the research says.