[Strawbale] Lime Stucco Primer, v1.4.1

[Speireag Alden]

A Lime Stucco Primer, v1.4.1

Hello, all.

     This is how I get from bagged, hydrated Type-S lime to cured lime 
stucco up on a wall.  I've done most of my own house, with good 
results, but I've done only my own house, so my experience is 
limited.  I hope that this is useful.

     For more information on lime, I highly recommend Charmaine 
Taylor's book on lime.  You can reach her at tms at northcoast.com.

---

How to Mix Lime Putty

     You will need:
         bagged hydrated Type-S lime
         an even number of five-gallon buckets
         a mixing stick or branch several feet long
         plenty of clean water

     Get some bagged hydrated Type-S lime.  Around here it comes in 50 
pound bags.  I've used GenLime brand and been happy with it, but I 
can't compare because I've never used anything else.  Find out when 
they took delivery from the lime plant, and don't buy any which is 
older than a month.  If you can, plan in advance and get your 
supplier to call you when it gets in.  I once got a batch where the 
sacks were still warm.

     You will need two five-gallon buckets per 50 pound sack of lime. 
Fill each bucket with the lime.  Add water.  As you add water, the 
lime will liquefy and reduce down.  Add water until it's easy to 
stir, with a branch cut to the size, or a grade stake, or similar 
piece of wood.  Add more lime.  Add more water.  Repeat until the bag 
is empty.  The level of the liquid should be a couple of inches below 
the rim.  Stir everything around and make sure that you've broken up 
any dry clumps.  Add a bit more water, if there's room.  Extra water 
won't hurt.

     Note that it's a very fine powder before and as the water hits 
it.  Some of it will puff up.  Either use a dust mask or use the 
lower-tech alternatives, as I do:  stand far enough away, or upwind, 
and it won't get you.

     Notice that I said, "the liquid".  This isn't lime putty yet. 
Let it sit for at least forty-eight hours, and don't disturb it.  You 
want things to settle.  It's usable after that, but the longer it 
sits the better it gets.  Presently you'll see that there's a layer 
of clear lime water on top, and inch or so deep, and below that it's 
lime putty down to the bottom.  Don't let it dry out while it sits! 
Add water as necessary if conditions are warm and dry.  Storing it in 
the shade will help.

     When you go to use it, *don't* stir the lime water back in. 
Instead, pour the lime water off into an empty five-gallon bucket and 
set it aside.  Scoop the putty out and use it for whatever, and if 
you need to add water to what you're mixing, use the lime water; 
you'll get a slightly better mixture that way than if you use 
ordinary water.  There's a bit of lime in suspension in the lime 
water, even if you can't see it.

     That's it.  Once it's sitting under water, it keeps forever, 
gradually getting better.  You can even let it freeze.  It may 
develop a sort of cottage-cheese texture and be harder to mix by hand 
if you let it freeze, but it will still be just as good once you're 
done mixing it in.  I mixed for about fifteen minutes and then got my 
hands in there and felt around for the last chunks, smashing them 
between my fingers.

     Easy as can be.  It takes me perhaps fifteen minutes to mix up a 
bag of lime.

---

How to Mix Lime Stucco

     You will need:
         lime putty
         masonry sand
         a stable wheelbarrow, preferably wide and shallow
         a five-gallon bucket
         a hoe
         a small bucket or container to use as a scoop.

     Pour the lime water from your bucket of lime putty into the spare 
five-gallon bucket.  Save it for later use.

     Take your scoop.  The size is fairly arbitrary, but something in 
the vicinity of a large yoghurt container will work, and that's 
exactly what I've used on occasion.  Pyrex measuring cups also work, 
but be aware that the sand will put visible wear on them, and you'll 
need vinegar to remove the thin layer of lime residue when you're 
done mixing.  Scoop about three scoops of lime putty out of the 
five-gallon bucket and into the wheelbarrow.

     Using the same scoop, scoop six scoops of sand into the 
wheelbarrow.  This isn't enough sand, but if you put all the sand in 
at once you'll find that it's hard to mix.  Use the hoe to mix the 
putty and the sand together.  I used a pointed hoe with a blade 
shaped like a wide leaf; I found that it was most versatile.  A 
standard rectangular garden hoe would probably have too big a face 
for easy pushing.  You can buy a mortar hoe, which looks just like a 
standard rectangular garden hoe but has a hole in the middle of the 
blade.  I'm sure they work fine, but a small-bladed hoe also works 
fine.

     So, now you've mixed three scoops of lime with six scoops of 
sand.  You have a mix like a thick soup, but less chunky.  Add three 
more scoops of sand.  That brings you to the proper ratio of lime to 
sand (1 lime putty to 3 sand, by volume).  Mix it in.  It will start 
to get hard to mix, especially if your putty is not watery.  Resist 
the urge to add water until you have all of the water pockets mixed 
in.  Then add a *little* bit of lime water.  Just a splash.  Let me 
emphasize that it's just a *little* bit.

     Have I mentioned that you only add a lit bit of water?

     Mix it all in again.

     Keep adding a *LITTLE* bit of lime water until you have the 
consistency you want.  If you run out of lime water, use tap water or 
other clean water.

     If you add more than a little water, then I guarantee that your 
mix will end up too runny, because it's very, very easy to add too 
much water.  If that happens, then you need to add a single scoop of 
putty, and follow it with three scoops of sand.  Take the sand from 
the driest part of the pile.  That will probably bring the 
consistency back to where you want it.  If not, keep adding lime and 
*dry* sand in the correct ratio *and no water* and the mixture will 
gradually get drier.

     If you're adding fibers, add them at the end, and mix just a bit 
more until they're evenly distributed.  Chopped straw works okay to 
control cracking, but fiberglass works better, is inexpensive, and 
inert in the stucco.

     What consistency do you want?  You'll get that from experience, 
but here are some guidelines:  if there are chunks, then you haven't 
mixed enough, or it's too thick.  If you drop a glop of it from the 
end of a shovel or trowel and it runs for more than about half a 
second after it hits the mix, it's too thin.  You should be able to 
pile it up in a pile which is at least half as high as the width of 
the pile at the base.

     Beyond that, I can't tell you more in print about consistency. 
You have to experience it.  Make a few batches and you'll notice that 
they're getting more consistent and easier to work with.  You'll find 
yourself halfway through laying the current load up on the wall, and 
you'll say to yourself, "Hey, this is a good mix".

     Lime stucco is very forgiving.  If you can't use it immediately, 
cover it with a tarp.  I've heard of people making enough for the 
entire job and then tarping it, and taking from the pile as 
necessary.  Unlike cement stucco, it won't cure until it's less than 
fully saturated with water.  Don't leave it uncovered in the sun or 
it will stiffen too soon.

---

Laying it Up

     You will need:  a mason's trowel (rectangular, with the handle 
mounted to the middle of one face, not with the handle sticking off 
to one side) and a hawk.  You can easily make the hawk from a piece 
of plywood or other thin scrap wood.  Just butt a cut section of 
branch up against the middle of the backside, and drive a screw or 
two through the thin scrap and into the cut section of branch. 
Voila.  You just saved yourself $15 for a hawk, and it'll work fine.

     Use the trowel to scoop some stucco up onto the hawk.  You can 
use the handle face of the trowel as a shovel, or you can set the 
hawk down against the board the stucco is sitting on and stroke the 
stucco up onto the hawk.  Either way, take a moment to center the 
stucco on the hawk so that your arm doesn't get tired any sooner than 
it needs to.

     Go to the wall.  Scoop a little stucco onto your trowel.  I can't 
describe it in print, but you'll soon figure it out.  Press it into 
the straw.  For the initial section, choose the stiffest section of 
straw.  Press it in hard.  Then add more stucco, spreading the patch 
of stucco, keying each new bit into the old bit.  That helps keep the 
stucco on the wall long enough for you to work it in again.  It also 
helps prevent the straw from rebounding and spraying you and the 
ground nearby with little bits of stucco.  I'm right-handed, so I 
like to start at the far right and work my way along toward the left. 
The mechanics are easier on the wrist.

     It takes some wrist muscle to key the stuff into the wall.  If 
it's not sticking well, make your mix a little wetter.  Don't worry; 
the second coat will be much easier to apply, because there's no need 
to key it into the straw.

     When you've done all you can for the time being, be sure to keep 
the stucco moist.  A fine fog from a hose is best for adding water. 
Anything more and you will move the fresh stucco, and damage the 
surface.  You can also cover it with plastic.  I have not done this 
myself, but I suspect that it would result in the best stucco, 
especially with judicious fogging with water.  It's just a pain in 
the rear under some circumstances.  Keep that stucco moist for as 
long as possible; several days at least.  Over the course of a week 
you can slacken off until you stop spraying it completely.  Weaning 
it from water like that will minimize cracking.

     It will also minimize cracking if you can prevent direct sun from 
hitting the fresh stucco.  If you have a tractor trailer or somesuch, 
park it so that it shades the wall.  Not only will it be cooler in 
the shade, but your finished stucco will be better for it.

     Once you lay up a layer of stucco, scratch the surface lightly, 
perhaps a quarter of an inch deep.  When it cures, that will provide 
a mechanical bond for the next layer to key into.  I used a wooden 
leaf rake which had broken; I cut the tines off at about the halfway 
point, and broke off every other tine, and I had a somewhat flexible 
tool with a long reach which I used to scratch everywhere.

     You should wait for the first coat to cure before you lay up the 
next coat.  Times vary depending on whom you talk to, but to be safe 
I wait a month.  It's worked for me, and I notice that the cracking 
(hairline, mostly) almost all happens over a week after I've put the 
stuff up.  So I'm skeptical that it would work well to put stucco on 
the older surface until at least two weeks have passed, and I would 
wait for a month.

---

     You can also pre-mix the lime stucco.  If you seal it in a bucket 
or some other securely airtight container, it will keep indefinitely. 
I have tried it.  It can be very convenient.  I haven't yet got 
enough experience with it to say for sure that letting it sit results 
in a better stucco, but I have heard others say so, and certainly 
what I got out of it was quite satisfactory.

---

Clean-up

     You will get the stucco on your hands, guaranteed.  I tried to 
use gloves, but it would soak through and actually suspend the stuff 
against my skin, making it worse rather than better.  I rinse my 
hands frequently, and always immediately after I put my hands in it 
(to fish something out or break up chunks while mixing).  I make sure 
to rinse under my wedding ring!  Every few hours I pour a bit of 
cheap vinegar over my hands and rub every surface thoroughly.  The 
mild acid helps neutralize the lime, which is very basic.  At the end 
of the day I put on a bit of moisturizer.

     That's it!

-Speireag.

-- 
Anger, if not restrained, is frequently more hurtful to us than the 
injury that provokes it.
--Lucius Annaeus Seneca, philosopher (BCE 3-65 CE)