Firstly I wouldn't be carrying out this job. Im notva tiling contractor. Second I dont think i said or even implied that you thought it was acceptable. Thirdly there are lots of primers. The one you should use is one that is suitable for the application. As for my superior knowledge... I was simply pointing out that there is a rule book. Its called the code of best practice... for tiling floors that is bs5328. Its supported by all sorts of othe documents put together by industry experts and manufacturers. Now please try to be a little less sensitive and a little less confrontational. I'm not here to have arguments...