Spun Glass. Another curious form of glass is the spun glass which is much employed in making fancy ornaments. Glass can be spun into a thread so fine and flexible that it can be worked into a fabric like any textile material. In this way, glass ties can be made by plaiting the spun glass threads into the required form. Spun glass fibre is used in making the brushes used for cleaning metals with acids. On account of its greater resistance to acids than is shown by ordinary cloth, an endeavour is being made to use spun glass cloth in certain industries as a commercial application. Spun glass is used for making a form of filter cloth which is being used successfully in filtering acid residues in certain chemical processes, and, no doubt, when the elasticity and strength of the glass threads can be more developed, the scope for its use in other industrial processes will be increased. The method of making spun glass thread consists in melting the end of a plain or coloured glass rod (which may be square, round, or triangular in section) in a blow-pipe flame and grasping the end which is melting with a pair of pincers, drawing it out and affixing it to a wooden drum, which is turned rapidly away from the glass being heated. The drum may be 2 or 3 ft. in diameter, and as the glass is continually fed into the heat it is drawn out into a very thin thread by the rapidly revolving drum, and coiled up until a sufficient quantity has been obtained. The thread is then cut across the drum, collected, and used for plaiting or braiding into the fabric or cloth. The iridescence and variety of colours yielded by the refraction of light between the glass threads gives spun glass its peculiar effect, very evident in the forms in which it is used in decorating small ornaments such as forming the tails of glass birds. Glass wool is made in a somewhat similar way, and is successfully used as a non-conductive packing material for insulation from heat. Glass frost or snow is made by blowing small gatherings of glass out to a bursting point. These very thin shells are then crushed and the flakes collected, and used for such purposes as surfacing sand paper or decorating Christmas cards, being sieved to the requisite size and affixed with a siccative to the paper.