On 17 Jan 2005, Christian McArdle wrote

So I'm planning to treat the artex with a Unibond-type of sealant
wash, then paint in the hope that the dark "follow-the-joists"
lines will be covered.

I wouldn't seal it. Unsealed, it is much easier to steam off and
replace with smooth proper plaster.

An excellent point, but it's a back, extra room which houses a spare
TV, ironing and overspill guests (we have a different primary "guest
bedroom"). So cleaning the artex off and plastering to make it look
that much nicer just ain't gonna happen in my lifetime!

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Cheers,
Harvey