Take advantage of modern sealing wax and put some ceremony and security into your writing!
Melt the wax at one end - but don't ignite or blacken - or heat a little in a spoon using a flame. Place the melted wax on the flap of an envelope and while it is still soft and warm, press the seal quickly and firmly into the wax. For the best impression the seal should be the same temperature as the wax.