Hi Laura,

There is a kind of varnish, it's called PRETEX !!!! It's a hardener and makes the papermache wetherproof.
I'm from the Netherlands so I don't know if you can get it.

good luck Andre

Hello
I'm Terry Bishop in Canada,
In answer to your question, can Papier Mache be weatherproofed, Yes...........Can Paier Mache be Waterproofed?.....well, can anything be 100% waterproofed??

You can weatherproof your works by coating several coats of boiled lindeed oil and baking in a 250 degree oven, if the piece will fit!!
You can also add Boiled Linseed Oil to your pulp during construction

Paint as desired, then give the item 4 coats of Marine Spa Varnish, even after all this, I would suggest a sheltered spot for your works, papier mache does NOT like ti sit in water!!

Reagrding the birdhouses, I have written with photographs a how to on Birdhouses that Jackie will have up and running soon, possible your failure is that you cannot get inside the birdhouse to weatherproof the interior!!  papier Mache will soak up water like a sponge

As a matter of interest, I make lots of Birdhouses and skip the Boiled Linseed Oil treatments, I love the way they weather, as do customers that give me repeat orders, my birdhouses are all backed on driftwoods and old worn bords etc and I do like the beaten up effect that I get with papier Mache

Hoping this helps
Terry

i would recommend yacht-varnish.