I am trying to patch up a bit of plaster that had got damaged but a leak from above which has now been fixed (dry for a couple of months). It was originally lime render but I have patched with sand and cement (5:1) with a plasticiser and was going to skim the whole wall after. My question is why has the sand / cement gone a sort of white colour as it's drying (see images)? Is this salts from the wall or something else and will it be a problem? It has set fine. Can I just pva and skim?
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