Original post by: phil ,
absolutely always use LOCA UV glue to properly re-adhere the glass. removing the lcd is very complicated because of its thin and long profile. Gold alloy wire is the safest way to remove the digitizer after you loosen the top edge enough to get it under horizontally. but you are quoting temperatures that are not safe. heat guns are risky and inconsistent. always use a hot flat surface no hotter than 100 f or 77 c. any hotter and you run the risk of burning out low temp colors starting with blue. as for LOCA glue, on the s4 apply roughly a dime width from 1/8 inch below the top to bottom right down the center. you always apply your glass starting at the bottom and slowly "press" the glue outward and up. the slower you lay the line of glue the less chance of trapping air, and never lift up on the glass and allow the glue to retract, it will get an air pocket. excess glue is easy to remove, any glue not under the clear glass will not get the same UV exposure and remains liquid, just use a small foam paintbrush dipped in solvent to clean around the lcd. it evaporates so fast it will not hurt the set glue on the lcd if you dont use too much.