How long I leave the TCA 40% on my skin and how I can neutralize? The results are better if I do a glycolic acid peels before?

Personally, I would not use 40% TCA on my skin, either at home, nor in my operating suites. Maximal I go to for a general peel is 35%, or even drop down to 30% with Jessner's solution and acetone scrub. I would recommend 8-10% multiple TCA peels, single coat (maximum of two at low low concentrations). TCA peels are self neutralising and v v v different to glycolic acid peels. Once TCA frosts- that is the end point of protein coagulation. All the best, Dr Davin Lim Laser and aesthetic dermatologistBRISBANE, Australia.