MG or Machine Glazed is an uncoated paper with shiny appearance on one side and a slightly rough surface on the other side. It combines high tensile strength properties of Kraft paper together with smoothness and shine for excellent printability. MG is an ideal base paper for a vast range of packaging solutions and is also safe for direct food contact. MG paper shows low grammage variation across the profile of the paper and hence exhibits very good machinability. It is often combined with other substrates such as polyester films and aluminium foil by the process of lamination for applications ranging from soap wrappers to chewing gum wrappers to butter wraps.
Some of the applications of MG paper are as follows:
Acid Free Paper
For packing Sarees, Fruits, Bangles, Gold etc.
Anti Rust Paper
Paper for wrapping machinery parts and also shaving blades to protect them from corroding.
Paper with high tensile strength, burst factor and twistability is required for making matchsticks particularly for waxed
matchsticks. The porosity and thickness of the paper are so controlled to ensure correct wax permeability which results in proper burning characteristics.
MG paper properties are further enhanced by the process of chemically refining the pulp and calendaring the paper.
The structure of the MG paper in itself is made of layers of cellulose fibres which are intertwined and circuitous. In the process of chemical refining, cellulose Fibers are fibrillated, swelled and collapsed, which increases the contact area between them. The pores between the fibres are thus closed resulting in better barrier towards moisture or air.
The process of calendaring involves the paper being run between heated rollers to smoothen it as well as to give it a more uniform thickness across the cross-section. The heat and pressure applied to the paper web by the rollers gives the characteristic Machine Glazed smooth high gloss finish to paper.
Calendering improves the barrier properties of paper by re-aligning the cellulose fibres and densifying their morphological structure, thus closing the pinholes in the surface which otherwise allow moisture or air to pass through.