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Our homes might be made of brick and plaster, our cars of metal and plastic, and our sheds and coops of lumber, but their surfaces – the part we see – are usually paint. Those flashy colours, though, often contain an alarming stew of ingredients – benzene, tricholoroethylene, formaldehyde, and many others – all of which flake off over time but never, of course, truly leave us. That’s not even counting the lead, now long banned, but which lingers in soil for generations.

So when our chicken coop needed some brightening, we took the old-fashioned route and whitewashed. Whitewashing was used on buildings here in Ireland into the late 20th century, only recently replaced by more dubious alternatives. Whitewash can consist of as little as two short ingredients – lime and water – that can be mixed and prepared with almost no energy in a few minutes. It is non-toxic enough that animals can actually lick it off with few or no ill effects, but antiseptic enough to discourage bacteria in the coop or dairy.

Lime refers not to the fruit or unrelated tree, but to a product made from burning limestone in a kiln. Limestone is mainly coral and shells of long-extinct sea creatures, squeezed over aeons into a solid mass of calcium carbonate, or CaCO3. When burned it vents carbon dioxide (CO2), leaving behind the volatile calcium oxide (CaO) or “quicklime.” When combined with water – hydrated or “slaked” – it becomes calcium hydroxide or Ca(OH)2, or simply called “lime.”

Humans have been creating lime this way for several thousand years, putting it to many uses; as a mortar for building, as an early form of cement, as an antiseptic ointment for animals or an anti-fungal coating for trees. A bit of lime could help remove hair from hides, sterilise water, bleach paper, deter slugs from a garden, or preserve eggs for months. It could be worked into boggy and acid soils to increase the fertility many times over. Also, it colours walls.

Its brilliant whiteness was valued here in Ireland, an island a thousand miles from the Arctic Circle where the winters grow very dark indeed. Cottages here were traditionally whitewashed in spring, as the rainy season gave way to the slightly less-rainy season, and again as part of the ritual leading up to Christmas.

The whitewash also showed too plainly when straw roofs needed to be re-thatched. After a decade or so, moss and algae build up on a straw roof, and when it rains the water runs off the roof and leaves green streaks down the whitewash. When a family had such visible stains, they were said to be “selling laces” – having money troubles, too poor to re-thatch.

Some old houses here were made with cob (sand, clay and straw mixed into something like cement) or wattle-and-daub (a mesh of flexible wood with a clay plaster coating), and as both were susceptible to moisture, the whitewash might have provided an early-warning system, showing where the owner needed to watch for erosion.

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After experimenting a bit, we settled on a rather simple recipe: 2 cups of water for every cup of lime, with a 1/4 cup of salt thrown in. It was a particularly thick ratio and flaked off a bit when drying, so next time we might try a thinner combination. Once mixed, the wash can be applied with regular paintbrush strokes – or with my 9-year-old’s more Jackson-Pollock-inspired approach. It looks thin and transparent at first, but whitens as it dries. Wear gloves and goggles – lime is only a mildly caustic alkalai, but work with it all day and you’ll get raw hands.  

We also tried mixing milk in as well, recommended by many old books, but found the effect no different, so the extra expense of milk was not justified. Milk powder, however, comes much more cheaply, and could hold some promise. Farmers here sometimes added oils – linseed was most popular – to make it more waterproof, or strengthened it with animal hair or cereal husks.

To be sure, whitewash has disadvantages; it is water-soluble, for one thing, so rain washes it away. This presents little problem when the sides are under a slight overhang, like the sides of our coop or most houses, but when it showers, our hen-boxes receive a gusher of water from the roof, and we had to divert the water with a plastic awning or the white coating wouldn’t have lasted long. Even in dry weather, however, whitewash flakes off over time, and powders your clothes when you rub against it. The good news is that it leaves no permanent stains.

It is also, almost inevitably, white – although in the west of Ireland, I’m told, some farmers painted their houses pink by mixing pig’s blood with the wash. The fact that lime was cheap and easy, while coloured paints were expensive, probably accounts for the classic look of Irish homes – clean white exteriors accented by brilliantly coloured doors and windows.

Locals here seemed familiar with many vegetable dyes or fabrics – elderberries for lavender; red cabbage or brambleberries for blue; nettles for green; St. John’s Wort for magenta; and marigolds, calendula, dock root and onion skins for yellow. Many of these colours are also water-soluble and fade quickly – which modern people think of as a disadvantage, although some valued the muted colours.

Some traditional peoples did create natural pigments, however, by boiling various clays and minerals – yellow and red ochre, sienna, umber, cinnabar and iron oxide for reds and browns, copper ore for green paints, urine for yellow, lampblack or charcoal created blacks and greys. Wherever you live, your plants and soil probably have their own palette of colours, which you can use at least as well as the Neanderthals who painted long-extinct animals on cave walls.

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