On Tue, 23 Aug 2005 18:27:29 +0000 (UTC), David Pearson wrote:

(a) coat both porous surfaces and join them together, or
(b) seal surfaces first with diluted PVA, allow to dry,
then do (a),

(b) is better, but (a) will do.

You can buy PVA in 1 or 5 litre containers at most builders merchants.

--
Nigel M