These olives in the photograph were picked from the same tree on the same day. Olives do not have the good manners to ripen all at the same time on the one tree; they will range in colour from green to violet to black (different degree of ripeness) and be of varying sizes.
There are many different recipes for pickling olives butI only have one small tree and in general I pick my olives when they are half ripened – no longer green, but not yet black – a violet colour. I continue to collect them in 2-3 batches over a week and pickle them by first soaking in fresh water and then in brine, but keep each batch separate and put each batch in brine in different jars. It is also not a good idea to process olives of different varieties in the same container even if they are at the same degree of ripeness – different varieties may require differing length of time for pickling and different methods. For example I prefer to cure ripe, black olives in coarse salt and then preserve them in extra virgin olive oil. For both recipes see: How to pickle olives
Sometimes to facilitate the water and brine to penetrate the olives more easily, I use a mallet to bruise them or make 2-3 slits on each olive or prick them with a wine cork and some sewing needles (see this home made implement in the photo above). These are called Olive schiacciate. I would recommend doing this with large olives.
These bright green, commercially processed olives in the photo below are called Sicilian olives in Australia. They are picked green and generally pickled with caustic soda (lye), but a kinder to one’s body and more environmentally friendly process is to steep them in a mixture of wood ash and water (but do not expect the same bright green colour).
It is important to use ash from untreated wood – not wood that has been contaminated by paint or treated with chemicals and preferably from a fireplace or wood burning stove in your own home.
I found the following recipe, Olives Vertes a la Picholine, in Preserving, The Good Cook/Techniques and Recipes, Time Life Books. The recipe is taken from a French publication: Encyclopedie Hachette de la cuisine Regionale by Celine Vence.
Once the olives have soaked in the wood ash mixture they are steeped in clear water for another period of time and then stored in brine that has been flavoured with some aromatics: a bay leaf, coriander seeds, fennel sprigs and orange rind. Coriander is not a Sicilian spice and apart from just using salt, you may wish to add just bay leaves and/or replace the coriander with fennel seeds. It you have opportunity to use the stalks of wild fennel, half your luck.
I have never used orange rind in the brine and prefer to use it in the dressing. You may wish to use the olives to make an olive salad.
I prefer to store my olives in sterile jars; I keep the olives submerged with some plastic netting (from a plastic mesh roll or gutter guard mesh) and always cover my olives with about 5mm layer of olive oil on top – this seals the surface and prevents surface molds.
When I am ready to eat the olives, I drain them and dress them with some extra virgin, olive oil and any of the following aromatics: crushed garlic, some of the green, fresh feathery part of the fennel chopped finely, thin strips of orange or lemon peel, fennel seeds, fresh bay leaves, crushed dry chillies. Steep them in the aromatic mixture at least overnight and keep them in the fridge.