Saturday, November 01, 2008

Documenting Strawbale 8: Natural Paints & Finishes

It's hard to believe, but we're at the point of deciding on paints and finishes for the strawbale addition! The outer walls of the strawbale have been wrapped with ty-par construction paper for the winter, and we'll finish the outside plasters in the spring when the weather is hopeful again. There are still the soffits and fascia to close up, making sure we keep all possible entrances for rain or critters impassable. So, now it's basically just the last stages of the interior building to be completed (final wall coat, window trims, floor, hook up electricity and last step of plumbing).

The top plaster coat is going on the walls today, and will hopefully be near completion by the end of the weekend or early next week. We've mixed a small portion of sand and finely chopped up hemp fibres into the lime coat to act as a binder. We read that other fibres such as animal hair, flax, and so on can also be used. Straw is too coarse for this coat. The top coat can also be tinted with natural pigments, or covered with a coloured lime wash afterwards.

While the top coat is drying we will start on the ceiling. We are covering the insulation/vapour barrier with tongue & groove pine boards, the same kind of boards with which we have built the window boxes. This wood should be stained or painted to seal it. We are experimenting with a hemp oil finish as sealant - it's available from either Hempola (directly), or through Homestead House in Toronto (they also do mail order). Homestead House also sells a variety of milk paints and no-VOC paints, as well as other finishes. Friends of ours just painted a basement floor with the milk paint, and finished it with a thin coat of hemp oil. They were very happy with the products and the service at Homestead House and recommended them. Homestead House website is:

As mentioned, we will finish our pine boards and earthen floor with hemp oil. However, the questions are what to colour the lime wash, if at all; and how to paint the drywall in the new bathroom and laundry area (in the board & baton portion of the addition). Does milk paint cover drywall? There are mixed reviews on this so we need to do a little experimenting. When we've come this far with mixing our own earthen plasters for the walls and floor, it would seem wrong to simply go and purchase a ready-made milk paint. I found some recipes for homemade milk paint (also known as casein paint) and will try them out, adding some natural pigment powders that I sourced at a papermaking supply store in town. We have a red (made from bloodstone), a green (made from clay), and a yellow (made from ochre). We could get really adventurous by making our own pigments with clay from here, or food items like vegetables, berries, dried crushed plants, tea or spices, crushed bricks, or coal, but then it would be difficult to keep the colour consistent.

Why use natural paints? We all know that conventional paints and woodstain emit toxins that are dangerous to our health, especially on the interior of a building in which we will be living (and breathing)! Exposure to VOC's (Volatile Organic Compounds) in paint can trigger asthma attacks, eye irritation and respiratory problems, nausea and dizziness among other symptoms. Prolonged exposure has been linked to kidney and liver disease and even cancer.

The old method of milk paints was used by pioneers, with basic ingredients like milk and flour. Originally it was made from organic raw materials: curdled milk, lime and a pigment. Homemade paints should be used soon after mixing. They can be refrigerated, but binding ability may diminish. As it's hard to make a consistent colour over and over, make enough of a batch of paint to use reasonable in one session. If using lime, wear gloves and goggles. Crumpled oil-soaked cloths can spontaneously combust, so they shouldbe washed before disposing.

Tips on what kind of paint to use on various surfaces:
Interior surfaces: flour, casein or oil paint
Exterior surfaces: oil, flour in mild climates, casein in extremely mild non-humid climates
Bare wood: oil, flour, casein
Stone: flour, casein
Bare drywall: casein, flour (but not over joint compound)
Wallpaper: flour, casein
Earthen plaster: flour, casein
Gypsum plaster: flour
Masonry (cement, lime, unglazed brick, unpainted earth): flour, casein, oil
Painted surfaces, or sanded: flour, casein
Surfaces that require frequent cleaning: oil

Flour Paint
1 cup flour
5 1/2 cups cold water
1 cup finely screened clay or other filler
1/2 cup additional filler (mica, etc)

Boil 1 1/2 cups water while you mix the flour and 2 cups water with a whisk. Once all lumps have been removed add combined water and flour to boiling water. Reduce heat to low. When it begins to thicken remove from heat and slowly stir in remaining 2 cups water. Combine the clay and powdered filler in a separate bowl. Add to the water/flour mix. Stir until desired consistency is achieved. Makes 1 1/2 cups paint.

Milk Paint
1 cups organic powdered nonfat milk
1 cup water
powdered paint pigment or dye (for colour)

Milk milk powder and water. Add natural paint pigments to colour if desired. Too much pigment will lessen the durability of the paint. This piant formula should dry to a glossy finish. After the paint has dried 3-4 hours you may top coat with varnish, oil finish, Pure Tung Oil, laquer, or beeswax. Try in inconspicuous area first, the colour may change.

Casein Paint
Made from quark has a soft, matt, chalky white finish and is commonly used on interior walls. Quark, will be in the cheese aisle at the supermarket.

This will make enough colorwash to cover approximately 4 square metres (43 square feet).

Start by "slaking" the pigment. To do this put some pigment in a bowl and mix enough cold water to make a smooth runny paste and leave to stand overnight. Some pigments do not mix easily with water so try a little alcohol (organic vodka) instead.

Put the quark into a bowl then stir in the slaked pigment. Add enough to make a usable colorwash. Stir regularly during use, as the pigment will tend to settle out.

This wash needs to be applied quickly to walls (milk goes sour). Once this paint is dry, any smell disappears (you may like to add some of your favorite essential oils to the mix). Apply to a clean wall, which has two base coats of white eco-emulsion. Use a wide paintbrush or large bath sponge and apply the wash with sweeping strokes. Allow the first layer to dry thoroughly before applying the next. Further layers will deepen the color.

Milk Paint with Lime

1 gallon non-fat organic milk
2 ½ oz Type S lime (available at hardware stores) Builders Lime also called Hydrated Lime (do not use Quick Lime).
2 ½ cups water
6 cups chalk (or other filler)

Leave the milk in a warm place for a few days to curdle, then pour through a cheesecloth-lined colander to separate. 2 cups of curds should be the result.

Mix curds and lime in a blender. Add a bit of water if the mix isn’t blending well and strain to remove lumps.

Add water immediately. Dampen and crush pigment and add to mix until desired consistency is achieved.

Stir in chalk or other filler. Makes 1 quart

Oil Paint

Oil paint is great for exterior surfaces and the oil painted surfaces can be regularly cleaned without damage to the paint. Oil paint takes a very long time to dry, in fact some never completely dry – this is the property that gives oil paint its elasticity which helps it move with surfaces as they naturally swell and shrink with the temperatures.

Organic raw linseed oil and a natural solvent such as citrus thinner are the typical ingredients for natural oil paints.
If you intend to paint bare wood and want to cover the grain of the wood, prime the wood prior to painting. This will help seal the wood against moisture and will create a better bond with the paint. Oil glaze can be used over flour or milk paints to increase their resistance to water and makes a nice stain with or without added color.

Oil Glaze
1 teaspoon natural pigment
1 teaspoon powdered chalk
2 tablespoons powdered chalk
1 cup raw linseed oil
2/3 cup natural solvent
Dissolve pigment and powdered chalk in ½ cup of linseed oil. Stir in remaining ½ cup of linseed oil.Add solvent and remaining 2 tablespoons powdered chalk. Whisk to remove all lumps. Makes two cups.

Oil Paint
Different pigments will absorb different amounts of oil, so exact recipes are difficult.
Pour 3 tablespoons linseed oil into a bowl and add pigment a little at a time until you achieve a dough consistency. Add more linseed oil until the mixture just begins to flow. Add solvent until the desired consistency is achieved. Strain to remove lumps.

Oil Paint Primer
Apply a thin coat along the wood grain. Remove excess with a cloth. Apply a second coat after first is completely dry, estimate 48 hours between coats.
1 pint raw linseed oil
1 pint natural solvent

Staining Wood with Tea and Vinegar

Tannins are naturally present in woods like oak, but pale woods like pine can be darkened by having tannins added to them in the form of strong black tea. Iron acetate (made with vinegar), when applied to wood, reacts with tannins to produce a rich dark color.

For tannins you'll need: 500ml of water and 25g Indian tea leaves.Boil the water and add it to the tea leaves. Allow the tea to steep for an hour or two, then strain into a bowl. Apply the mixture to the wood with a medium paintbrush or lint-free cloth; allow to dry. You'll find pale woods will be colored by this alone; if not then apply the iron acetate.

For iron acetate you'll need: a large wad of fine wire wool and malt vinegar. Place the wire wool in a jam jar and cover it with the malt vinegar. Screw the lid on and leave overnight. The next day, strain the mixture through a colander or sieve lined with muslin or cheesecloth to remove all the wire wool. Apply the iron acetate solution to the wood with a medium paintbrush or lint-free cloth. The wood will darken for up to half an hour. Allow to dry thoroughly before lightly sanding.

Clean Coatings of the Future

Chemicals used in conventional paints and coatings leach into the environment and can cause air pollution as they dry. However, nanotechnology could be the answer. Sally Ramsey, founder and vice president of new product development at US-based nanotech company Ecology Coatings, says new, paint-like coatings are the future. Made up of tiny particles with innovative characteristics, they're sprayed on and cured (or dried) using ultra-violet light, removing the need for a solvent.The result is a coating with no polluting characteristics. Nanotechnology can deliver other benefits such as scratch resistance, waterproofing or anti-mold capability - all without adding toxic chemicals.

The Natural Paint Decorator, by Lynn Edwards and Julia Lawless, published by Kyle Cathie. The Natural Paint Book bridges the information gap, offering an in-depth explanation of the differences between conventional and eco-friendly paints. Illustrated throughout with full-color photographs, the book provides complete instructions on how to make all-natural paints and finishes at home, using readily available ingredients such as clay, gelatin, linseed oil, and artist pigments.

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