The following is taken from the book reprinted by D. Harris, The Handbook
of Horticulture and
Viticulture
of
Western Australia By A. DESPEISSIS, M.R.A.C. THIRD EDITION 1921.
No. 1.― BORDEAUX MIXTURE (Full Strength for Winter Spraying).
Sulphate of Copper (bluestone) ... ... 8lbs.
Quicklime (freely slaked) ... ... ... 4lbs.
Water ... ... ... ... ... 22gals.
(a.) Dissolve the bluestone in 10 gallons of water by placing it in a sack suspended in the water and moving the sack about, when the sulphate will quickly dissolve. (b.) Make a whitewash with the lime, strain to separate the grit, and bring the milk of lime to 10 gallons. Mix a and b, and make up to 22 gallons. Use only wooden or earthenware vessels. When the foliage is out, use the half-strength mixture by diluting in double the volume of water. To determine if the mixture is safe to use on tender foliage, insert a new nail or the blade of a penknife for at least half a minute; if copper is deposited on the steel, lime must be added.
Another test is the Ferrocyanide Test:―Add a few drops of a strong solution of yellow prussiate of Potash (Potassium ferrocyanide).
If lime is lacking, and if there is an excess of sulphate of copper the mixture will turn black, but it will show no change of colour if the quantity of lime is sufficient.
Sulphate of Copper dissolving in a tub of water.
No. 2.
The same with a small quantity of molasses added. How much?
No. 3.
The same as Nos 1 or 2 with 44 gallons water. Half strength for tender foliage.
Following the search for Bordeaux mixtures for commercial use in vineyards, I researched several papers.
These are quite dated as it is possible that post WW2 all papers written on copper sprays are proprietary.
So I had to develop my own. This is what I now use. Take the above recipe and convert to metric and then reduce the strength so that the copper sulphate used is 2.5 grammes per litre.
Now here's the trick #1. Lime! Don't use builders lime in dry powder form unless you have no alternative. What you require is a silica free lime in liquid form (lime putty) used in the plastering industry.
In Western Australia Susac Lime (Susac Lime Supply Pty Ltd 377 Karoborup Road WANNEROO WA 6065 - More... ph: 08 94075056) can supply 25 L drums at about a $30 per drum.
Method as above for 4.0L.
Weigh out 10g of copper sulphate and place in a 10L bucket with 2.0L rain water. Preferably leave overnight to dissolve or use warm water. These days the crystals are quite fine and clean and so filtering is not required.
Fill spray tank with about 3.0 L water. Add copper solution and stir.
Weigh out about 8.0g of liquid lime and then add to 2.0 litres rain water. Mix thoroughly to form a homogenous cream. Add to spray tank, rinse container with rain water into spray tank. Top up tank to 4.0L.
Now here's the trick #2. Check the pH of your mixture. You should aim for pH neutral, ie pH = 7.0. If the pH is less than 7, you can add some more lime. If you don't have a pH meter you can use the Despeissis method above.
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