Color developing colorless primer

An essentially colorless primer for use in preparing a plastic object for bonding with a solvent cement, the primer comprising an organic solvent capable of at least partially softening the surfaces of the plastic object to which it is applied and an essentially colorless color-forming chemical in the solvent,

• the color-forming chemical being capable of being activated by at least one of the plastic to which it is applied, by a component in or on this plastic, by ambient conditions to which it is exposed when applied to the plastic or by a developer included in a subsequently applied solvent cement,
• activation causing the color-forming chemical to develop a visually noticeable color thereby identifying the surfaces of the object to which the primer has been applied.

A solvent cement for use in bonding a plastic object with another object, the solvent cement comprising an organic solvent, a thermoplastic resin dissolved in the organic solvent, and an essentially colorless color-forming chemical in the solvent cement, the color-forming chemical being capable of being activated by a developer contained in a complementary primer to be applied to the surfaces of the plastic object before the solvent cement, activation causing the color-forming chemical to develop a visually noticeable color thereby identifying the surfaces of the object to which the primer has been applied.

A solvent cement for use in bonding a plastic object with another object, the solvent cement comprising an organic solvent, a thermoplastic resin dissolved in the organic solvent, and a leuco dye developer comprising an acid-functional organic resin.