Glass glue, replacing the Canadian balm.
20 g very light rosin dissolve in 100 cm3 of toluene or xylene in a tightly closed vessel, shaking frequently. Dissolving takes 2…3 days. Leave alone for a long time, so that the undissolved particles sink to the bottom, which lasts several days. Carefully decant the clear solution into the evaporating dish, cover with a piece of tissue paper and leave at room temperature to evaporate excess solvent. The finished glue should have the consistency of rare honey. Pour into a jar with a polyethylene or polyamide screw cap.
Glass objects to be glued should be carefully degreased and thoroughly dried, then warm it up slightly. Apply a thin layer of glue on both surfaces to be glued, press down lightly, remove air bubbles by slightly shifting the glued surfaces, press more firmly in the right position and leave for 2…3 days. Adhesive prepared on toluene dries faster, than prepared on xylene.
The glued areas remain perfectly transparent, if the rosin used was almost colorless. This adhesive is suitable for gluing optical elements (prisms, lenses), crystal glass dishes, for sticking coverslips of microscope slides. The joints are resistant to water and alcohol, not resistant to hydrocarbons and elevated temperature. The tearing strength of the glued joint is low.