Dissolve about 1 g of agar in 100 ml of boiling water and allow to cool to about 50 °C. To 5 ml of the solution add 5 ml of trinitro-phenol solution (1 g of anhydrous trinitrophenol/100 ml of hot water).
Približno 1g agarja raztopimo v 100 ml vrele vode in pustimo, da se ohladi na približno 50 °C. 5 ml raztopine dodamo 5 ml raztopine trinitrofenola (1 g brezvodnega trinitrofenola na 100 ml vroče vode).