Any plumbers/bathroom fitters about - need some advice please. can you stick mastic to mastic. I went round the edge of the bath the other day (have shower over so it gets really wet) and I missed quite a large bit. It's all dry now. Can I do a new bit over or do I need to scrape it all off and start again? It's really important it doesn't leak because we are a flat and it would drip down to the flat below.