Show hints about Cemen tm A certain amount of time murt bo be allowed lowed for or all cements cement to bar harden ders and the time varies with mill the nature of the cement used the 11 portland ortland cement journal illustrates the point thus lor for instance it if an oil cement I 1 is used a great deal of time x ill be ue cesary but lot if one that lq is li liquefied quelled by heat beat is used u ed the object v ill be ready for use a BH 4 boon us as the joint becomes cold cola there Ls Is however the objection to such cements that they are liable to come aam t when the fici aln abed i job is ia again exposed to the heat beat on the other hand the cements compoi composed ed of oils and metal like hire or red lead and boiled oil become hardened by oxidation and cannot again a tin be softened by any ally usual mean cleans A neat great dejl deal of tune time it needed for buch cements loser to set but once tin is thoroughly lone done they will stand almont tiny climate or treatment copal varnish and ordinary hh elliK make excellent cements cement but require from two to bix day days to set alt abor duglay |