Laura - on Google - there is a gal on Etsy that sells the flowers using the carnival glass - perhaps you can contact her and ask how they hold up... Most crafters are happy to share information...

Thanks. I finally got a response on the garden junk forum. She said she has had a carnival glass flower outside for 4 years and it is doing good so I'm going to go ahead with it. Most of the sellers on etsy are very helpful, including me, but I hesitated to ask for info from a competitor. I don't do well with rejection. lol
Thanks for your response.

I collect the carnival glass,platesin antique shop are like 80 dollars