This is a very interesting culture which reliably produces yoghurt of good quality with very simple operations. It is astonishingly robust. We have had this particular kefir since 1998, but it seems identical to one which we kept from 1982 to 1996 without problems.
If want to start making your own kefir, then we may be able to send you some of our brave little troopers.
In the package you will find some soft granules, looking a bit like badly overcooked cauliflower florets, in a few spoonfuls of milk.
(i) Put the culture in a glass jar with milk, not airtight.
(ii) Leave it around until it's ready.
(iii) Put it in the fridge until you want to use it.
(iv) Pour through a sieve (helping it along with a spoon) to separate the grains from the yoghurt.
(v) Resist the temptation to wash the grains under the cold water tap, as this is known to adversely affect their growth. Put them back in a clean jar with fresh milk.
(vi) Drink the kefir.
You do not need to heat the milk. You do not need to keep the culture at any particular temperature, though of course its growth will be more predictable if you always leave it in the same place. You do not need to sterilize anything, just keeping things very clean will do. We have been making kefir since the late seventies and only once or twice had what seemed to be a mild contamination, which spoiled the flavour a little for a week or so, but the culture has always recovered. When we go on holiday, we just freeze the grains, with or without milk, in a little plastic container. Our record for successful recovery of a frozen culture is just over a year.
We recommend using a glass jar so that you can judge the progress of the fermentation from the outside. We find that a good tablespoonful of the grains, in a 1 liter/ 2 lb glass jar, on the kitchen windowsill, gives an agreeable yoghurt in about 48 hours. But you may find that you prefer a milder or stronger yoghurt. The culture will grow and as soon as possible you must do a freezer back-up, after that the offspring can either be passed on to friends or composted. Now for some details. The particular dose you have in the film canister that we send you is a starter pack, and we suggest experimenting with half-pints of milk for the first couple of cycles, using shorter rather than longer incubation periods, while you find what suits you. For the sieve, we use a deep metal sieve with a 1 mm mesh but other people might prefer plastic.
A word of warning: after periods of neglect - either in fridge or freezer - the culture is a bit slow and not perfectly reliable for a couple of cycles, and you may want to start it up gently with short cycles in small quantities. A thick velvety layer on the top of your kefir is a sign that it is ready to be eaten.