I see that many folks, including myself are frustrated by the fact that MDF has an annoying tendancy to expand and spoil, be it with veneered or more severly with sprayed and painted finishes.
Some folks have suggested PVA/water mixes, shellac, level filling, resins etc.
I've tried most and still get the expansion to a greater or lesser degree but finally I have found something that truely works.
Its actually used for stabilising rotting wood and uses the moisture within the wood to actually form a chemical bond that looks the fibres in a resin cast that penetrates into the MDF. Once set its water proof and very tough, much tougher than untreated MDF, which also means I'd suggest you do all you sanding and detail work before applying this as it will cause you some extra work. Its excellent for applying spray finishes onto though as its almost like steel in its substrate toughness.
The one that I used is Bonda Wood Hardener:
http://www.decoratingdirect.co.uk/viewprod/b/BONWH/
I'd also highly recommend using void free plywood, its better than MDF by far for jointing and for absolute troublefree finishing use the wood hardener on this also.
Hope this helps folks out there, who like me, probably pull their hair out when they try to spray cabinets when faced with this problem.
Some folks have suggested PVA/water mixes, shellac, level filling, resins etc.
I've tried most and still get the expansion to a greater or lesser degree but finally I have found something that truely works.
Its actually used for stabilising rotting wood and uses the moisture within the wood to actually form a chemical bond that looks the fibres in a resin cast that penetrates into the MDF. Once set its water proof and very tough, much tougher than untreated MDF, which also means I'd suggest you do all you sanding and detail work before applying this as it will cause you some extra work. Its excellent for applying spray finishes onto though as its almost like steel in its substrate toughness.
The one that I used is Bonda Wood Hardener:
http://www.decoratingdirect.co.uk/viewprod/b/BONWH/
I'd also highly recommend using void free plywood, its better than MDF by far for jointing and for absolute troublefree finishing use the wood hardener on this also.
Hope this helps folks out there, who like me, probably pull their hair out when they try to spray cabinets when faced with this problem.