Dale Lynch of Palmerston North asks :-

How do I make a coal-flower garden like my grandmother used to make?

Alan Happer, a chemist at the University of Canterbury, responded.

Coal gardens were very much a fad in the 1930s, and, since this was the time of the great depression, they were sometimes known as ‘depression gardens’.

In those days all of the ingredients were readily available in almost all homes — water, salt, coal, ammonia, and laundry blue - but few homes will have them all today. Some say un-iodised salt is better than iodised. Ammonia containing soap ('cloudy ammonia') you can still get, but the clear sort may be more difficult to come by. Lumps of coal may be becoming a vanishing species in most homes, but the real sticking point is the ‘laundry blue.’

Older people will remember Reckitt and Colman's ‘Blue,’ which came in the form of a small cylindrical lump sealed in a cloth bag. This was a blue dye, a pigment called Ultramarine. With time, white cotton clothing and sheets acquires a faint yellowish tinge. When blue was added to the wash something already white acquired a very faint bluish tinge, which one didn’t normally notice. However anything that had a slightly yellowish tinge lost this and looked white. Today 'Blue' has been replaced by modern dyes that absorb UV light (invisible to us) and re-emit it as a light blue. These are added to the laundry detergent we use and the term ‘whiter than white’ today is a reality rather than a marketing exaggeration.

One can still buy ‘blue’ in the USA in the form of `Mrs Stewart’s Bluing Solution.’ Her 'blue' is ferric hexacyanoferrate (we know it better as Prussian Blue). This is not very soluble in water, and exists in the solution as a colloidal suspension of tiny particles. The `Mrs Stewart's' web site claims that these particles assist crystallisation of the salt from the solution by encouraging crystals to form on them. An ordinary blue dye would dissolve completely and there should be no particles present to do this.

Most of the coal flower recipes are very similar. The basis is a strong salt solution (about twice as much total liquid as salt by volume is about right.) To this you add about a tenth the volume of ammonia. (Why is not exactly clear.)

Some people recommend adding small amounts of food dyes or something similar as well. The whole is poured over lumps of coal (don’t cover them completely) and left to evaporate. What you basically end up with is lumps of coal coated with coloured salt crystals. The coal is not really essential – it can be replaced by barbecue charcoal or even small pieces of brick. You can feed your garden from time to time with more solution.

For complete details on how to make a ‘coal flower garden’ I would advise searching the web using Google under ‘coal garden.’ There are lots of recipes. Happy hunting.

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