Whitewash source or recipe in Canada?

I've got my coldshed working, and probably wont ever render it. It's in the middle of a spruce grove, has 4 foot overhangs, and doesn't get wet.  But I do want to apply a coat of whitewash to make it look less ugly.

Now, from Wikipedia, whitewash is hydraded lime and finely powdered chalk.  Other sources say add salt to make it bind better.  And yet others say 1-2% linseed oil.

Any pointers to best way to paint a bale for the short run?

You mean like a coolshed as pictured below.:

I thought that a layer of plaster had to be put on both inner and outer walls on the straw.

Like that, but with bigger overhangs.

If you are building a straw building, yes, normal practice is to put plaster on both sides.  If you are retrofitting an existing building, I don't think you put plaster on the back side.

In my case I don't intend to put plaster on it at all.  

however, a few coats of whitewash will make it look a lot better, reduce the number of critters taking up residence, and keep the straw stuffed in cracks still.

As a kid I painted many a barn with whitewash.  Back then we took a bag of lime adding it to a bucket of water.  

Looking on the internet it appears that they are saying "Hydrated lime, also known as builders or masonry lime. Make sure you don’t get garden lime because this is a different substance.
Fine grade salt and water.

Maybe what you want is something else?

Common recipe

* 2 c salt
* 6-8 c slaked lime
* 1 gallon water
* Mix salt in water.
* In part of the water mix the lime until it's a stiff paste.  Add water slowly.  *Think gravy*.  Making it thick initially keeps lumps from forming. Add the rest of the water.

Whitewash will look very thin on application.  Multiple coats 1-3 days apart work better than single thicker coats.  This allows the carbonation of the hydroxide to proceed.  If done in warm dry weather, the use of a binding agent that slows drying is necessary, or misting the coat.  

Recipe 2:  This one is low in salt by comparison to most.

* 12 c lime
* 2 c salt
* 4 oz elmer's glue.

Recipe 3:

* 12 cups lime
* 4 cups salt
* 2 gallons water

For additional durability: ONE of

* 2 tablespoons powdered alum OR
* 1/2 cup hide glue flakes OR
* 1/2 gallon skim milk

I suspect the glue gives the best durability increase.

From de Gruchy's Lime Works

A Lime Whitewash / Colorwash Recipe

* 10 lbs St. Astier Natural Hydraulic Lime 2 (NHL 2)
* 2 gallons of water
* ¼ cup of casein powder dissolved in hot water
* ½ cup of Borax (Won't allow mold & helps repel insects along with the lime)
* 3 lb common table salt (Salt is proven to only be beneficial to lime whitewash to harden it. Don't use salt
with any Portland Cement based materials.)
* ¼ teaspoon laundry bluing for extra whitening or approximately ¾ lb of iron oxide pigment for a color
of choice.
* Add 1 oz Alum to help make the pigment become more colorfast

I've also seen 1-2% linseed oil added as a binder, up to 1/8 raw linseed oil for the liquid.  

A whiter colour and increased mildew resistance may be added by adding copper sulfate.  This does make the paint more poisonous in quantity.

***
Traditional pre-made whitewash had fine chalk. (CaCO3) Since whitewash 'hardens' by Ca(OH)2 + CO2 => CaCO3 the addition of chalk reduces the amount of hardening needed. Too much chalk however and there's not enough binding to hold everything together.  Chalk doesn't need to be roasted in its making so it's a lot cheaper.

Wikipedia https://en.wikipedia.org/wiki/Whitewash

Good article:  http://pachamamatrust.org/f2/1_K/CBu_build/Se01_whitewash_KBu.htm

This latter mentions several other binders, and is oriented somewhat to conservation applications.

This may or may not interest you.  I use a lot of "purchased" milk paint but this link talks about making your own.   Milk paint was used quite a bit during the colonial period and it's pretty tough stuff once cured.

Milk Paint with Lime

I like the concept---small building built and insulated with straw bales.

Where I am, I think I'd have to plaster both in and out.  Packrats and mice on the inside.  Deer on the
outside....maybe cover the outside with hardware cloth.  The deer where I live have no problem ripping
thru 6-mil silage plastic with their hooves.  The numbers are incredible some years.  Several year ago I
threw out some moldy oats onto a nearby field.  Within 30 minutes I had a herd of over 30. Wintertime
can be a bitch up here and the slightest whiff of hay could attract a small herd.

While searching for something else I ran across this thread that might help:

https://permies.com/t/68520/plaster-finishing

Bryant RedHawk wrote:It sounds to me like it was a lime putty that you describe.

Lime putty can be made with hydrated lime, salt will act as a hardener. The recipe is simple, water, lime, sand, salt if desired. Mix the lime and water till you get a "loose batter" consistency then add sand to thicken, or you can simply use the lime putty with out any sand.
The salt would be added after you have the consistency you desire for spreading with a stucco knife, it doesn't take a lot of salt should you want to use it.

I never mix this stuff by measuring I put 2-3 gal of water in my wheelbarrow then start stirring in lime from the bag, when I start getting trails from the wood paddle I use I add sand until I can just see grit in the mix.
If I'm not able to spread it right then, I add water until the putty is covered, it will store like that for weeks if necessary.

Redhawk

I DO NOT WANT TO PLASTER THIS BUILDING.

Plastering is a hell of a lot of work.  A plastered bale wall is 300 pounds per linear foot.  I don't have foundations for that. 50 feet of wall means 15,000 pounds of plaster.  That's 6000 pounds of lime, and 9000 pounds of sand.  

This was a preliminary concept.  I took a 12x12 shed and applied a layer of bales to the outside.

This is a test building to try out a bunch of ideas:


A: Can I keep a room of ice until spring?

B: Can I keep the walls dry with an overhanging roof.

C: Can Unplastered strawbale be used for utility sheds, with only a thin coat of lime (1/16 to 1/4 inch) to reduce air infiltration and give it moderate fire resistance.

This concept doesn't work for a house.  With a house, you have too much invested in the rest of the house in addition to the bale shell.

For a shed it's a lot easier:  The bale wall becomes a disposable feature -- you think of it like paint or siding.

I've taken this approach with other things.

I have a deck that consists of 16 deck blocks 4 16 foot 2x4s and 6 6x6 foot pallets.  it took 1 day to build.  I expect it to last 10 years, then I will replace the wood.

Nothing lasts forever.  What effort gives maximum return with minimum work.


I have a round bale of flax in my woods that is over 20 years old.  It's a foot shorter than it was. Decomposing from the bottom.

Sorry, I was just trying to be helpful.

Plaster applied one inch thick weighs over 10 lbs per square foot.  An  8 foot wall 50 long would have 4000 lbs of plaster just
on one side.

Interesting specification to keep in mind...1/8-inch hardware cloth might be all that would be needed for my situation.....

Note to self--add to list of projects.

The usual plastering recipe is 3 coats of at least 1/2 inch.  

And my figures were for plaster both sides.   The 300 pounds per linear foot figure actually includes the bales.  My bad.

your 10 lbs / ft2 is a minimum too, as it ignores the amount of of plaster used to key into the straw.

But:

Even 4000 pounds of plaster is more work than I want to do.  I want to get it down to 500 pounds. Max.  (1/8")

This building is already too small.  So the goal is to do the minimum possible.

I can relate to the desire to do less work. If you mix your limewash on the thick side (and add some fine sand and a pozzolan), especially for the first couple of coats, it will fill and bridge a lot of the voids in the surface of the bales and effectively perform as a plaster. Then you can follow this with a thin top coat or two, and renew that every couple of years if you feel like it.

Has anyone used an airless paint sprayer with limewash? This would really cut the labour investment down. Obviously, you'd need to leave sand out of the mix if you did this to avoid destroying the sprayer.

I have a wagner that I'm going to try using.  

I also have a lee velley tools venturi sprayer.that I will try.  It has the feature that the air stream blows across an upright pipe so there are no moving parts.  Works best for thin stuff.

If I can spray fast enough that it only takes half an hour a coat, then I'm not as concerned about it take a zillion coats.

I'm very interested in the results!

I've used a lot of whitewash.  The simplest mix is just Type-S lime (hydrated lime) and water - but that will wash off with rain.  The binders will help make it stay on during wet weather.

I have never tried it on something like straw, although I've done a lot of wood, like 2x4s.  Lime and wood, and also straw, are not chemically compatible.  Lime is extremely alkaline, and straw is more like wood, so I assume it's slightly acidic.

So the limewash will not want bind to it chemically, nor will it want to stick to it super well.  I say this with much experience applying limewash to wood...it makes flakes that want to flake off. Versus when it's applied to cement, to lime putty or another chemically compatible surface - in that case, it creates a chemical bond.

I would try tests with different binders added - linseed oil, salt, milk, tallow, ox blood if I happened to have a bunch for some reason, etc. Whatever you can find that might work. Test several mixes, let them dry and then spritz them several times with a hose, let dry, spritz again, and see which lasts better.  I would do this on a separate "test" bale of straw, if you have one, so you aren't hosing your building down.

I'm not sure if it will work, but that's how I'd go about it.  Good luck!

Here's a website with more suggestions.: How to Apply Limewash from Limestuff.co.uk  They name linseed as the binder of choice for weatherproofing.

Hi S.G.  and others!

I work as a mason in Canada.  Haven t tried to render/parge/whitewash straw but it would be similar to mineral wool which we often exolate with and then render/stucco.

The Heritage recipe for lime mortar( whitewash in our climate would be with more water added) is as follows:

1 part white portland cement( grey is fine but will be "off white")
2 parts hydrated lime( calcium hydroxide)
8 parts fine sand( get play sand which is also available in white)

Mix the ingredients dry. make a hollow and add 1-2 parts water to mix well . THis is mortar , if a wash is desired more water is added carefully to give a paintable consistency. Stir often as you work.

This being said you will need to put a "scratch coat" on the straw. THis can be the same type of mortar  but not too runny. We use a square concrete trowel to apply this. just pull it on from the bottom and upwards. How thin it goes on depends on the smoothness of the surface. Don t play with it as you work or it will sag and fall off. It takes some experience but by the end of it you  should be good at it.
THe scratch coat will be dry enough to whitewash in 24 hours.

I would apply the lime mortar with the same trowels and using a wet brush gently brush the surface moving the brush in random movements and all the time making sure the mortar is dry enough to be brushed without sagging or running but not too dry , as it will then be too hard to brush. The brushing closes the surface making it more durable and gives that pleasing look like old monastary walls.

The portland is the hardener and must be included. Lime without a hardener is useless and will never dry . I Don t like the adding of salt to any mortar. Portland is the best .
Home Hardware has these products but make sure the bags are loose and not hard or lumpy.
We also generally apply the fiberglass mesh to the scratch coat .
The way I make scratch coat where stickiness is required is  :  Into a wheelbarrow   6 shovels of masonry sand, 2 shovels of standard Portland cement( 1:3) and 1/3 bag of standard thin set mortar( tile mortar)  .Mix dry ingredients well with small spade, then make a hollow and add 3/4 washbucket clean water and mix . add more water as required. If sand is very dry you will need more water or less if sand is wet/damp.
Scratch coat can also be "thrown " on. You use a brick trowel and flick it at the wall , it should stick well, good on uneven surfaces.

I hope some of this helps. Work on one wall at a time and proceed carefully and don't leave it too long between stages.  

Just to add-

An easy scratch coat/base is made with ready mix  if sand and sement is too much work/ trouble.

The combination I use then , is 1 bag quickcrete Sand Mix to 1 bag quickcrete Mason mix , if more stickiness required 1/3 bag thinset mortar .

The ready mix is dusty , sand and cement isn't. The ready mix will cost more in the end but will be convenient. Uses more water due to dryness but this makes a nice smooth and very strong base for any finish. Also not  that thick depending how it takes to the underlay and how well it is mixed and applied.  I get it down to 1/4 inch , but thats with alot of experience, and I suspect the straw will require more, but just follow the contours, that will only enhance the appearance.

I don't think it would spray very well.

I will point out I'm not trying to plaster this building.  Just paint it.

If you want the coating to breathe and not trap water vapour in the straw then I would avoid portland cement. There are pozzolans which can be used to modify lime (most commonly in mortar or plaster forms) and speed its hardening without sacrificing the important quality of breathability.

Pozzolans include things like volcanic ash (the "secret ingredient" in Roman cement), brick dust, and wood ash. I use wood ash frequently, since it's easy to get. You could try adding it to your paint mixture and it will make the limewash set more quickly and will also make your scratch coat tougher.

Sprayability is dictated by the fineness of the sand and the fluidity of the mix along with nozzle size.  Any cement product is sprayable. As long as the surface to be sprayed is clean and you don't overload it it will be fine but it will require alot of air.
You might be able to rent the equipment in your area. Worth a look. Whatever fine mix you choose should work. I would just trowel it on or splatter it on.

Re: Portland cement.

It is the most frost tolerant. Important in Canada. Pure limebased mortar is famous for disintegrating in our climate in an outdoor application.
No other objections to lime mortar, that is why we use 50/50 mixes alot too, as mentioned above by mixing 1 bag sand mix(portland based) with 1 bag masonry mix(lime based).

Phil Stevens wrote:If you want the coating to breathe and not trap water vapour in the straw then I would avoid portland cement.

I agree with Phil. Avoid Portland cement for your application, to keep the breatheability and to keep the cost ($ and embodied energy) down.

Many whitewash recipes posted. I used the simplest one on my house in Wisconsin and it stood up well, no mold or sloughing off in the rain. That was over six years. I used two coats. I don't see the need for lots of salt. Wood ash, that sounds like a cheap/free additive. Fly ash can be hard to source.

My recipe: cheap ag hydrated lime from the local feed store, water, and a bit of salt-- much less than a cup per five gallon bucket. I looked up the water:lime ratio. I used one part lime to eight parts water by volume. This isn't critical. The first coat can be more dilute, 1:16 (good for first coat). Thicker coats can be 1:6 if you want, and if you can still spray it.

I like the sprayer idea. A mud/texture sprayer would do it if you don't want to run whitewash through your Wagner airless.