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How to Make Bordeaux Spray

Step by step instructions to make 10 litres of 1% solution

One of the great advantages of Bordeaux spray is that it can be inexpensively and safely mixed at home with two easily obtainable ingredients, copper sulphate and hydrated lime. Copper sulphate often sold as bluestoneis is available at hardware stores, garden centres and rural produce stores while hydrated lime is widely available and often called builders lime.

Quite small quantities of ingredients will make many litres of spray. This is just as well as plants should be thoroughly sprayed to the point of runoff.

To make 10 litres of Bordeaux spray at 1% concentration you will need the following:

  • 2 buckets of at least 10L capacity
  • A garden sprayer, a course nozzle will reduce blockages
  • 100gm of copper sulphate crystals
  • 100gm hydrated lime, a white powder
  • a piece of muslin cloth around 1m square

Bordeaux spray is mixed in two stages. To make a 1% solution dissolve 100 grams of copper sulphate in 5 litres of water in one bucket and 100 grams of hydrated lime in 5 litres of water in another bucket. Warm water will help ingredients dissolve more easily. Then, while stirring, pour the lime mixture into the copper mixture. A cloudy blue-coloured liquid results.

To make larger quantities increase the quantities in proportion, eg. to make 20 litres of spray use 200gm of lime and 200gm of copper each mixed in 10L of water.

The key to successful spraying is straining the resulting mixture through muslin cloth to remove larger solid particles that can block spray nozzles. For best results strain twice. First strain through two thicknesses of muslin cloth when pouring the lime mixture into the copper solution. Rinse the muslin in cold water, fold it over the top of the garden sprayer and pour the complete lime/copper mixture into the sprayer. Remember to continuously stir while preparing and agitate while spraying as the mixture can quickly settle out. It is best used within 24 hours of mixing


Step 1: Measure ingredients accurately.


Step 2: Stir 100gms of Limil thoroughly in 5 litres of water.


Step 3: Stir 100gms of Bluestone in 5 litres of (warm) water.


Step 4: Tie muslin over top of bucket of copper solution.


Step 5: Keeping lime well mixed, pour into copper solution.


Step 6: Rinse residue off muslin in cold water.


Step 7: Stir lime and copper mixtures together thoroughly.


Step 8: Place rinsed muslin over top of garden sprayer.


Step 9: Keep mixture stirred, pour into sprayer, agitate during use.