Best sealant for acrylic paint / paper-maché?

June 14, 2012 11:02 AM

I'm augmenting my bike helmet with a bit of paper-maché and acrylic paint. What should I put on as a final layer to make it water proof?
posted by Squid Voltaire to Sports, Hobbies, & Recreation (9 answers total)

For rain, you COULD just get one of those rain covers and slip it on, removing it for non-rainy times.
posted by Danf at 11:27 AM on June 14, 2012

I'd let your final layer be the acrylic paint, and I'd use that tough texture spray-polyurethane stuff (Rhino-liner is the brand name I am thinking of, but that is a service provider. You can get this stuff at any of the home improvement stores or K/Wal/Tar/Etc. Comes in a big spray can) as the intermediate layer between the maché and the paint.
posted by dirtdirt at 11:37 AM on June 14, 2012

I would use some decoupage varnish or lacquer, although I'm not sure how weather-resistant it is as a material.
posted by Think_Long at 11:48 AM on June 14, 2012

I would leave your helmet alone. They aren't really designed to work with the extra stuff on them that you are putting on.
posted by OmieWise at 11:50 AM on June 14, 2012 [5 favorites]

Best answer: The guy who taught me to make papier-mache heads [example] told me that Rustoleum spray lacquer is the best, and so that's what I use. It will repel light rain and mist though the whole structure will eventually soften because, you know, it's made of paper. Spray lacquer will also darken your paint job some so test it first.
posted by komara at 12:05 PM on June 14, 2012

Yes, check your helmet instructions. Mine specifically said not to attach anything permanent as it can make the helmet less effective in a crash andnot to put chemicals like paint on it as the foam inside can be invisibly damaged by the fumes. This is a seriously bad idea from a safety standpoint, IMHO.
posted by holyrood at 12:12 PM on June 14, 2012 [1 favorite]

Also, anything that decreases smoothness could snag during a fall, causing a rotation injury to the neck. Helmets are smooth for a reason.
posted by scruss at 12:19 PM on June 14, 2012 [2 favorites]

I've used varathane as a sealant on both papier mache and polymer clay. It's designed to be a wood sealant for outdoor decks, among other things.
posted by lilywing13 at 12:26 PM on June 14, 2012

I know it is frowned upon to paint or otherwise mar youth baseball batting helmets, as the manufacturers will not guarantee the safety of a helmet so modified. I'd be worried about the same thing here.
posted by stevis23 at 5:37 PM on June 14, 2012