Head retention is adversely affected by the following:Glassware has residual detergent or grease.Young beer can produce a large foamy head that quickly dies away.Too much simple sugar (sucrose or dextrose) in the brew.Low carbonation level in the beer.A racing ferment due to high temperature.To check your glassware, get some clear (crystal type) plastic glasses from the supermarket. Pull one straight out of the plastic wrap and place it beside your favourite glass. Fill both with the same brew and compare head retention. Head retention can usually be improved by adding around 300g of maltodextrin to the wort. Replacing some of the sugar/dextrose with malt extract will have the same affect, with the added bonus of extra malt flavour.