In 1930 at an international conference on painting conservation, a heated worktable – ideal for lining - was introduced. The table – known as the hot table – was made of a large slate slab, heated and maintained to about 50/60°C by means of adjustable heating elements that insured the uniform melting of the adhesive (wax-resin). In 1955, the hot table was improved by combining it with a system of vacuum pressure providing for both complete heating and complete pressure. Today, this is the widely used vacuum hot table. The most recent and perhaps the most interesting advance in the sector of the use of vacuum pressure – is the technique of pressure lining without the use of heat ("cold lining").