I've been doing some cake designs that play off of the colors and finished found on art glass recently. I have a Pinterest board called "decorative things" and I realized that most of the things on them are art glass and that type of art nouveau style.
Depending on what look you want on the finished piece, you need to use a combination of layers of luster dust paints on either white or colored fondant and gumpaste pieces. This pink cake started out white and was painted with multiple layers of pink, pearl, and silver Pearlized Crystal Colors dusts diluted with vodka.
Remember that if you're painting color onto a surface that could be eaten, the color should be edible. Crystal Colors are FDA approved for food use.
(The scrollwork molds used on these cakes can be found here: https://www.etsy.com/shop/ACakeToRemember/search?search_query=scroll+mold&order=date_desc&view_type=gallery&ref=shop_search)
This cake was done using black fondant to begin with, and painting with grey, blue, pink and green lusters. Because you start with the darker fondant, you're going to get an extra color in there that's visible, but hard to figure out where it's coming from at the same time. Starting with a darker color is going to require more layers of color to get to where you want it to be, but it will also force you to build up layers that will end up being more reflective.
The decorations on this cake were done with black gumpaste painted with paint made from silver luster dust and vodka.
To do cakes with this type of finish, you need to use a wide brush so that you can cover large areas without creating edge marks. I recommend those black foam brushes to avoid brush marks and the possibility of the brush dropping bristles onto the cake.
The washes should be fairy thick, because you want the color and not a watery drippy mess. Don't make them too thick, though, unless you want a more opaque type of shine.
This cake had a more opaque look to the flowers and leaves because I used Rainbow Dust Edible Paints on them. I HIGHLY recommend these paints for a really good shine, but if you want something that isn't opaque you'll have to thin them down. I hadn't used these before this cake, but I was very impressed with the shine and coverage I got from them, and a little went a long way. Use my affiliate link here to see their products on Amazon: Rainbow Dusts
Also look on my Pinterest board for cake tutorials for a step-by-step visual tutorial on how to make the roses and thorns cake.
Kara Buntin owns A Cake To Remember LLC, online cake supplies at www.acaketoremember.com and www.acaketoremember.etsy.com