Recommend a primer for tiling plastered / painted wall?

[White Room]

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Hmmm interesting. I haver to admit I thought Sirapite was a Lime based plaster but it appears from research it was indeed Gypsum based (similar to plaster of paris. I do know it contained cellulose and petroleum additives so I shall do some research ans see if I can come up with an answer.

It may be to do with the direction of the sulphate rich moisture. with the gypsum being at the outside surface the sulphate laden moisture would be towars the outside so these sulphates have less contact with the cement. I shall come back to you on this. To date I can find little information on Sirapite Plaster. [/COLOR]

Last time I used it was 23 years ago, it's actually pronounced siraphite but obviously spelt sirapite ???