Requesting recipes for non-toxic, garden-friendly “white wash”

Using flat white surface coatings in the garden is helpful in hot climates. White reflects light that plants need without absorbing heat. White surfaces enable garden areas to remain cooler in the hot sun. Cool surfaces reduce evaporation and plant stress. I’d like to “paint” landscape surfaces such as tree trunks, concrete walls, pavers, stones and wooden built structures with a DIY coating that is non-toxic: no oils or latex. It is okay for the white to wear off in a few years when I’ll just “white-wash” the surfaces again. Please share your recipes and experiences with non-toxic outdoor white-washes. Thank you!

I have whitewashed barns using this same recipe:

https://permies.com/wiki/138186/PEP-BB-naturalbuilding-sand-whitewash

Thanks for this important link and info about slaked lime, Anne. This is the "real" way to white wash and natural builders need to know about this professional  and beautiful approach. As the label indicates in one of the photos, calcium hydroxide solutions are extremely corrosive and can cause chemical burns. I'm looking for the kid-safe approach using ingredients like flour paste, baking soda, white clay, maybe borax, diatomaceous earth, white sand, maybe perlite (don't breathe this stuff!), maybe toilet paper or cotton, egg shells or other super safe ingredients. All of the recipes on Google searches that I've found are for indoor recipes. These may be fine but someone may know of a good way to make an outdoor coating that will hold up pretty well.

I don't know anything about "calcium hydroxide" or which picture it was in.

What we used was plain old lime that we mixed with water and put on horse barns. Came in sacks that said "lime" which was then mixed with water.

I was just a kid and don't remember any burns.

I am fairly certain what we used was this:

Lime is a calcium-containing inorganic mineral composed primarily of oxides, and hydroxide, usually calcium oxide and/ or calcium hydroxide. It is also the name for calcium oxide which occurs as a product of coal-seam fires and in altered limestone xenoliths in volcanic ejecta

https://en.wikipedia.org/wiki/Lime_(material)

Maybe this thread will offer something you like:

https://permies.com/t/149767/ideas-toxic-finishes-pine-board

Maybe some other members will offer something better.

Anne, calcium hydroxide is what's in the bags in the BB pics, and there's a prominent warning visible on the bags about it being strongly alkaline. I think that's what Amy is referring to?

It's still quite alkaline (pH >11.5) even when mixed to limewash strength, and premixed limewash comes with a serious warning in the UK. Despite that, limewash is a fabulous product and I intend to limewash my house. I'm sure the burns etc referred to would need prolonged contact with limewash. But it might not feel suitable to a parent wanting something their kids can safely use. Personally, I'd rather use limewash than something containing borax!

Like you we did a lot of things when we were kids - were even made to do things when we were kids, by our dear loving parents! - that are now considered dangerous!

Calcium carbonate, garden lime, is a very different thing and has a pH about the same as soap. It might be usuable as a temporary limewash that would need frequent renewing. But it doesn't have the same chemical reaction as it dries that makes proper limewash or lime renders a good wall covering.

We whitewash our barn with slaked lime, it is not very dangerous, it's a food additive (E526) You can stick your hand in the bucket and stir it, and drips on the skin that sit there for hours before being washed off don't do anything Once it sits on the surface it reacts with the air and changes it's chemistry becoming even more inert. It does wear off in about a year and a half of rain.

I would avoid getting it in your eyes, but we don't use any protection with it at all once it's diluted down. it should look like skimmed milk before you apply it and it looks clear when it goes on, only changing to white as it dries.

Maybe I'm way over reacting to chemicals but I've avoided lime because I've heard about the extreme care needed to avoid eye and skin burns. This picture links to the label that says, DANGER EXTREMELY CORROSIVE:
https://permies.com/t/138186/a/147595/01A7DDA8-F837-41FF-BE79-720296ECAE1D.jpeg
I'll bet that you were one tough kid, Anne!

Amy, once calcium hydroxide is well diluted, it is a lot less corrosive. And once it's mixed, as it ages, it becomes less corrosive, I think. The concentrated powder in the bags does need care to minimise contact and avoid getting it in the eyes. I see recommendations for wearing gloves and eye protection when applying limewash.  Once it's on the wall or tree, it would surely be kid-safe.

Skandi, I loved the pics of your fab barn limewashing job! Was that well-aged limewash or freshly mixed?

Amy, this is a great question and I will be curious to hear if there are other solutions.
While the dry lime is definitely hazardous, I think lime wash is fairly safe, so long as you use a respirator, goggles and gloves while measuring and mixing the dry lime. Once it is mixed, it is mostly harmless, from my understanding. I recently lime washed my chicken coop. I didn't wear gloves while painting it on and got quite a bit on my hands. No burns, maybe a bit drying.
I put a bit on the outside of the coop too and it has held up okay so far. I imagine if it was on a building under an eve, it would hold up for awhile.
Obviously, if you were to put it on pavers or trees, it'd be good to know your soil pH, since obviously, lime is quite alkaline.
There's some great info on limewash here: https://www.5acresandadream.com/2014/05/amish-whitewash.html

Jane Mulberry wrote:Amy, once calcium hydroxide is well diluted, it is a lot less corrosive. And once it's mixed, as it ages, it becomes less corrosive, I think. The concentrated powder in the bags does need care to minimise contact and avoid getting it in the eyes. I see recommendations for wearing gloves and eye protection when applying limewash.  Once it's on the wall or tree, it would surely be kid-safe.

Skandi, I loved the pics of your fab barn limewashing job! Was that well-aged limewash or freshly mixed?

It comes mixed with a bit of water here, and you then need to dilute it further before use. but it is "fresh" if you want it aged it costs a lot more, though apparently it gives a more brilliant white effect.

Slaked lime has been used for centuries, to preserve eggs, for human consumption, and I have approximately 10 dozen preserved that way, right now, in my pantry. I've used it to whitewash my porch swing, in the past, and plan to, again. It inhibits the growth of moss, works as an antimicrobial, of sorts, and has other preserving properties. But, not all limes are created equal. I use the food grade slaked lime, available in the canning department, at the grocery stores, and have never even tried the stuff in those big bags.

Amy, I am sorry that you have not gotten an answer to a safe paint for your garden.

I was sure that if "Permies" used whitewash in that PEP Badge that it was safe to use.

It is my understanding that Lime is made from limestone and since I live where limestone is very prevalent especially in my well water I thought it was a safe product.

I hope Judith's thread offered you something you could use.

I have heard of milk paint do you feel something like that would work for outside?

I have read so much here on the forum about safe paints I feel certain that someone will speak up and offer you something that you can use.

This information about lime has been incredibly helpful to me - thank you all for the education! I thought that I had overcome most of my trepidations about building materials but really, I have uninformed ideas about lime. The posts and links to facts have been really informative and I appreciate hearing about your experiences.
Yes, I will try lime for a future project where preservation matters.
For my current project, alkalinity is a real problem. I need something gentler, a white coating that is earthworm safe when it erodes. The link that Anne provided in another thread https://www.realmilkpaint.com/ is helpful. Milk paint is a good possibility here. What about using white bone meal? Anyone ever try diatomaceous earth? Flour paste seems like a good binder but I don't want to attract critters to the garden.

Here is a DIY recipe from This Old House https://www.thisoldhouse.com/painting/21528976/all-about-milk-paint

...(C)onsider making your own milk paint. Some recipes require you to curdle milk for 24 hours (1/2 cup of lime juice, lemon juice, or white vinegar to one quart of skim milk), then strain out the curds and mix the whey with pigment powder (available at art supply stores or online from resources such as the Earth Pigment Company). Don a face mask for protection when using the finely powdered pigment.

A quicker recipe uses powdered milk: Combine ½ cup milk powder, 1 teaspoon of pigment, a dash calcium hydroxide, and two tablespoons of water in a container or dedicated blender and mix very well. Double or triple the recipe as needed, but remember that milk paint has a short shelf life so only mix as much as you intend to use at a time.

This sounds great for a small project but I'd like to mix about 5 gallons then slosh it around on concrete surfaces to lighten them up. That is why I'm leaning toward flour paste as the binder instead of milk. Bulk garden ingredients for the color components are cheaper than artist's ingredients.

Amy, I've seen recipes using a basic flour paste recipe and white or coloured clays thinned with water for painting house walls outdoors, but only under the shelter of wide eaves. This is a long but good video about this: https://www.youtube.com/watch?v=qZvEHTQ90yA

It would be interesting to try it with white kaolin clay and see how long it lasts exposed to the rain! Would love to hear a report back on how it works!

Jane, that video is gorgeous! I love this kind of natural sourcing of material and walking into nature to harvest materials. This is incredibly inspiring to me and I really appreciate your search.

The the proportions look similar to what Bill and Athena Steen describe in this Mother Earth News article
https://www.motherearthnews.com/diy/recipe-for-clay-paint-zmaz01amzsel

For every 1 part starch paste, dilute with 2 parts water. That will make the paste liquid enough to permit adding the other ingredients.
Next, add enough colored clay or white kaolin clay with pigments to achieve a consistency that will spread easily with a brush. It is difficult to describe, but we look for a mixture that will cover in two coats. The right consistency will be like thick cream.

Like you said, Jane, the white kaolin should be perfect. The "other ingredients" could probably include a small amount of garden ingredients for future soil considerations: sand, straw, bone meal. I'm going to mix this up and paint some practice stones to see how they weather over the winter. I'll let you know how it goes.

Today (Nov 12, 2021) I "painted" several sample objects to determine how well they will hold up this winter: an adobe horno, concrete garden pavers, a vertical stucco section, smooth basalt rocks, bubbled rough lava rocks, rough weathered pine and smooth pine. Winter here is occasional snow or rain amounting to about 1.5 inches. Night time freeze and day time thaw are typical for most of December - January.
The test paint recipe is made of 1 quart each: boiled flour paste, sand, clay, and water. The sand and clay are from deposits on the property. I sifted both with 1/8 inch hardware cloth wearing a fine particle mask while sifting (the fine particles contain silica). I mixed the gallon of coating with my hands (its all natural),  and used a brush to apply it. I applied the coating onto misted substrates and dry substrates (none were pre-cleaned of existing dust (since I'm using the same dust in the mix): dry application was much easier. I'll compare long term adhesion of wet and dry surfaces. The coating for this test is light brown like the sand and clay here. If this holds up, I will buy kaolin and white sand instead of yard material. So far the coating on all surfaces is adhering well and filling in substrate cracks nicely. There is no cracking in the now dried coating on any substrate.  This was a fun project with easy clean up.

Anne Miller wrote:Amy, I am sorry that you have not gotten an answer to a safe paint for your garden.

I was sure that if "Permies" used whitewash in that PEP Badge that it was safe to use.

It is my understanding that Lime is made from limestone and since I live where limestone is very prevalent especially in my well water I thought it was a safe product.

Slaked builders' lime that you use to make whitewash is perfectly safe.  In the sense that is not toxic to humans or animals.  It's not terribly toxic to plants, either... but having said that, I wouldn't just pour my leftover bucket into the soil.  It is distinctly alkaline, as mentioned above.  That is the reason for the warning labels, and also the reason to avoid using it as a soil drench ; )

I built my own home by hand using lime plaster, which I applied by hand.  And I can tell you for a fact that you will get chemical burns from lime in contact with your skin.  But it takes hours of exposure.

Some simple precautions are all you need to use it safely.  Wear goggles or otherwise avoid getting it into your eyes.  Stop every 20 or 30 minutes to wash off your hands and arms, preferably with a weak acid solution (highly dilute vinegar) to neutralize any lime, and you will be just fine.  I would actually recommend doing this over wearing gloves, as the gloves only ensure that any bits of lime that find their way down inside stay in contact with your skin.

So in general, white wash is nothing to be afraid of, and likely a good choice for the OP's garden project.

Diluted with water, the water base latex paint ( if you have any left overs)  can be used as a white wash on plants etc . That's what I did on trees (cherry, apples, plums, rose canes, wood decorations and so on) as we had left over white flat ceiling paint, and an white, gray wall eggshell latex paint. It may not be perfect but it's better than throwing it in a land fill and it's non toxic .  

Just to add to the body of experience on slaked lime and lime wash: it *is* corrosive but it won't harm you unless you're using it a lot.

Painting with lime wash I found to be incredibly enjoyable - it's tactile and the colour change is really nice to observe. Also, any splashed can be quickly wiped off. Just wear eye protection.

I have also mixed lime-infused cob and I found this much less enjoyable. Whilst mixing it with my feet for several hours I noticed that I had literal holes being burnt into the skin of my feet. It was exacerbated by the presence of small stones in the mix but, yuck, don't do this! Neat, undiluted lime is quite unpleasant and you'll want to wear protective clothing.

A further note is that lime, when cured, becomes limestone and is both incredibly long-lasting, completely inert and it re-sequesters any carbon driven off during its production.

after using lime  ( lime putty or  hydrated lime) - either as a a 3:1 plaster mix or in a lime wash, you can rejuvenate your hands by

coating  Hands with butter then  with some sugar ( whilst butter is still on)  leave for a few minutes then towel off.

or

before doing the work

apply Amolin create ( baby nappy rash stuff) on your hands

the above helps to reduce hands drying out and cracking.

as too a limewash recipe

strawbale house book
&
millers plastering : plain and decorative
have some recipes
&
www.lime.org