A freshly prepared agar slope should have a light covering of yeast growing on a moist agar surface. Old slopes dry out leaving the agar as a hard, shrunken solid mass which only allows poor yeast growth. Slopes which are shrunken or cracked are likely to have fewer viable yeast cells which may ferment poorly.

Well prepared slopes should survive for up to 6 months if kept in a refrigerator and tightly stoppered, allowing you to keep stocks at hand for that unexpected brew. However some strains are more sensitive to ageing than others. Remember that dark storage is preferred, and essential if the agar was made up with hopped wort, as yeast cells can be damaged by light and the hop chemicals, even in such small quantities, can carry a skunked flavour into your brew. (However if the little man in the fridge is working the light will go out!- Eds)

One agar slope cannot contain enough yeast cells to prime a 5 gallon (22.5 litre) home brew. For this size brew a starter culture of 1 pint (500 mt) is recommended as necessary. Use your agar slope to inoculate 1 or 2 pints (500 ml or 1 litre) of sterile wort and allow it to grow for 24/36 hours at 20-25oC.

Making up a 2 pint (1 litre) starter enables you to split this into 2 or 3 batches to start more than one brew, making the slope more cost effective. The unused starters can be kept in the fridge for a week or so before pitching into the next brew.

Transferring yeast from a slope to a starter should be easy but occasionally cells adhere tightly to the surface. This may be a feature of the yeast strain or the age at the slope. Fresh slopes tend to have looser ceils which can be released by pouring a little of the sterile wort into the slope and shaking the bottle. This is the recommended method for the first use of slopes. A more advanced method, similar to that used in laboratories, will be explained in a further article.

Open and close your agar slope bottles in clean conditions with clean hands and avoid touching the bottle rim. Pour wort carefully to avoid spillages. Shake the starter bottle to get the wort to absorb as much air as possible to encourage yeast growth but carefully, to avoid over frothing. Some home brew shops stock an anti-foaming liquid and a drop or two of this is useful as it will stop your starter foaming out of the starter bottle without spoiling your final brew. lf you have a camping stove or blow-lamp, light this and carry out all your yeast and starter manipulations within 9 inches, as this will sterilise the surrounding air. Most laboratory yeast handling is done in a normal room but close to a Bunsen burner.

This article is designed to encourage home brewers to begin using fresh, proper brewing yeasts available on agar slopes. A future article will explain further techniques, including making your own slopes to store your own yeasts. Of course, several home brew shops now stock American produced liquid yeast packs but for success these have to be made up in a starter, so using agar slopes is no less convenient.

The only source of fresh yeast agar slopes in the UK, as we go to press, is Brewlab, Darwin Annex, University of Sunderland, Chester Road, Sunderland SR1 3SD. The strains available are Ale, Mild, High Alcohol, and Lager and they come with full instruction for their use. The cost is £2:50 per slope, including post and packing. Instructions for use and information about the yeast strain will be included. Freshness is guaranteed -and you will then be confident of making real beer. After all, having gone to the trouble of using good quality malt and hops you don't want to use inferior quality yeast.

The Alemaster Zymopure yeasts mentioned in Graham Wheeler's latest book, Brew Classic European Beers at Home' are not yet available.