1. When to harvest

The olives should be picked when, while still green, they have reached their maximum size, before they start to turn a barely perceptible pale yellow colour. Therefore, depending on variety, producing area, type of cultivation (irrigated or dry-farmed) and the season that year, they may be harvested from late August up to the first ten days of October.

2. Grading and washing

The next step is to grade and wash the olives, before placing them in a lye solution.

3. Preparing the lye solution

In times gone by olive or oak ash was used, or even lime, but lye is almost always the norm nowadays.

Twenty or 25 g of lye are used for each kilo of olives. When it has been dry-farmed, 20 g is the proportion used, while when rainfall has been normal or the trees have been irrigated, 25 g is what is needed. This is because of the different water content in the two cases.

Once it has been settled how much lye is required per kilo of olives, fill a container - it can be made of plastic, wood, tin-plated aluminium, terracotta, etc.- with 1 litre of water to every kilo of olives. For instance, if we want to pickle 10 kg of olives, we need 10 litres of water, to which we add 250 g of lye if the 25 g proportion is required. As the lye dissolves in the water an exothermic reaction makes the water heat up, and the resultant solution must be left to cool before use.

4. Soaking the olives in the lye

Now put the olives in the lye solution and stir them round with a wooden spoon or spatula to wet them completely. The fruit will sink to the bottom of the container, but some will float to the top. This should be avoided since otherwise the part of the olives that is not immersed in the liquid will turn brown. If after being coated in the solution, the olives come into contact with the air and absorb carbon dioxide, the sodium hydrate will be turned into carbonate. This chemical reaction is what makes the fruit a dark blackish colour rather than leaving it a uniform green. This drawback can be avoided by covering the solution with a galvanised tin, aluminium or other type of lid so that the olives are completely immersed in the solution and are thus kept away from the air.

5. How long to soak the olives

Apart from the factors we have already mentioned (dry or normal year, irrigated or unirrigated, etc.), the time the olives should be left in the solution varies, being contingent on variety, olive size and flesh thickness. Generally speaking, they should be soaked for 8-12 hours. Exactly how long is determined by testing the olive every half hour after 8 hours have gone by. The idea is to check how far the solution has penetrated the flesh. The diagram shows how this is done: slice the fruit halfway down its length, i.e. at its equatorial point, to see what the flesh looks like. It will have two concentric circles; the outer circle will be darkly coloured and the inner one will be lightly-coloured. We know the olives have been soaked for long enough when the solution has penetrated halfway through the flesh. If the outer area accounts for less than half the flesh, the olives obviously have to be plunged into the liquid again and re-tested half an hour later.

6. Removing the olives from the lye

When the time comes to remove the olives from the lye, we will find that the solution is very dark. Either the fruit can be lifted out of the solution or the liquid can be run off, this depends on the equipment available. The main precaution is to avoid touching the olives with one's hands. Once this has been done, soak the olives in clean, pure tap water. More water should be added than was used in the solution, the aim being to remove any residual lye as well as any other undesirable compounds. When the water turns dark, change it and carry on in this way until the water is clear and clean. At this point it is wise just to test the fruit again.

7. Seasoning the olives

When the olives have been almost completely washed, prepare the seasoning. Put water in a pan -the equivalent, in litres, of two-thirds of the weight of the olives-, add 20-25 g of bayleaves, 10-15 g of dill, and the rind of 3-4 medium-sized lemons, all of which should be roughly chopped. Then boil this mixture for about 2 hours to allow the aromas of the ingredients to flavour the water. Leave it to cool.

8. Preserving the olives

Arrange the seasoned olives in well-washed containers, made of glass, terracota and any other material; the jars should have a long neck and an airtight lid. Pack the olives up to two fingers below the edge of the lid and then fill the container right up to the top with the seasoning liquid. Remember to filter the liquid before pouring it over the olives. Store the olives in a cool, dry place. They are now ready to be eaten. If you want, leave them for a few days to let them absorb the full aroma of the seasoning. After a fortnight, it is wise to run off the seasoning liquid and to cover the olives with clean water, to which 25 g of salt are added for every kilo of fruit.