Hi, need some advice! I have a huge grey cement block garden wall, the wall is not rendered so it is rough, though i have painted a few coats over some parts of it. I want to mosaic directly onto it. What adhesive should i use? It needs to be very weather resistant, the wall is very high so gets full sun and wind and rain, temperatures between minus 11 °c in winter up to high twenties in summer. I have made a small mosaic out of pebbles just putting cement directly onto the wall this week- i hope this is weatherproof and doesnt crumble off! So, should i use just cement for all the tile mosaics straight onto the wall? , will it last, will the adhesive or cement take differently to the painted part of the wall? and has anyone tried this before? Thank you!

I apologize if this isn't the right place to ask this question but I will ask it anyway. There is a DYI video on You Tube that was put there in 2013 that shows a man making a wooden press for making bars of soap out of old pieces. It shows not only the small press he built but also shows him making a new bar of soap out of the pieces he cut. At no time did he say to add water and yesterday I made the press and added the cut pieces, but when I picked the bar up it crumbled into nothing. Does anyone know how I can get that done? Should I add some water to perhaps cause it to stay together? Thanks for any suggestions. Rich