Is there a way I can be sure of success with powdered gelatine?
Always ensure that gelatine is properly dissolved – failure to do so is perhaps the commonest cause of problems. Sprinkle it into a small basin containing 3–4 tablespoons of liquid and leave it to soak for a few minutes. Then place the basin in a pan of barely simmering water and allow it to dissolve completely – you can test this by dipping in a teaspoon and turning it over to see any undissolved granules. Don't let the mixture get too hot. Strain the mixture before using it.