The 'barrier' is usually a resin material bonded between the outer and inner layer of the pipe itself.
Some artists create their toys using synthetic resin material and resin casting.
Using a resin material, thermal ribbons print a higher quality document that doesn't easily smudge.
Since the 1960s, resin materials have been used for all types of bushing up to the highest voltages.
In 2010 concerns were made over the stability of the sculpture and that the resin material might disintegrate.
The material used prior to this development was a self-curing resin material.
This resin material was mixed first and then placed in the tooth.
The development of this new technology gave way to new light activated resin materials.
The resin material is easier to paint than the softer and more slick vinyl often used for other types of dolls.
They will be made of the same resin material as the other aforementioned products.