178 DISEASES OF GLASSHOUSE PLANTS 
Mixture was entirely the result of an accident. In order 
to prevent loss by thieving, the vineyard owners near the 
city of Bordeaux were in the habit of sprinkling the vines 
near the roads with verdigris to make them look as if 
they had been poisoned. Later a mixture of lime and 
copper sulphate was used to replace the verdigris on 
account of cheapness. Downy mildew, caused by 
Peronospora viticola, was introduced accidentally from 
America, and it soon became apparent that the vines 
sprinkled with lime and copper sulphate were less affected 
by the disease than those untreated. Bordeaux Mixture 
is prepared by mixing a solution of copper sulphate and 
lime in varying proportions in accordance with the 
disease and kind of plant to be sprayed. 
Standard Bordeaux Mixture is made of 6 lbs. copper 
sulphate, 4 lbs. of lime and water to make 50 gallons. 
The copper sulphate should be fully 98 per cent purity 
and the lime should be freshly burnt stone lime of good 
quality. The copper sulphate should be dissolved in 
40 gallons of water in a barrel, and the lime slowly 
slaked in another vessel. This is best done by adding 
as much water as the lime will absorb, but no more. The 
remainder of the water, making 10 gallons in all, should 
be added gradually to the slaked lime, taking care to stir 
thoroughly at the same time. The 10 gallons of lime and 
water are then added to the 40 gallons of copper sulphate 
solution, stirring all the time. No matter what quantity 
of the mixture is being prepared it is necessary to strain 
the materials through a sieve, the best type being made 
brass wire having 18 to 20 meshes to the inch. 
Correctly prepared Bordeaux Mixture possesses a brilliant 
sky-blue colour, but the improperly prepared mixture 
generally has a greenish colour, and is dangerous to use 
as it will injure the foliage. The following precautions 
must be observed in preparing the mixture: 
(1) Only pure 98 per cent copper sulphate and freshly 
burnt stone lime should be used. Air slaked lime is 
useless. 
