The more I travel and the more antique shops I venture into, the more I am convinced that no one knows what true period water gilt is, or how to recognize it. Most pieces on the market today have had repairs so finding true period water gilt is rare, and it makes the price tag quite different from the later Dutch metal or paint.
Period gilt is whisper thin layers of true gold leaf applied onto gesso, typically over wood, with a sizing. While that might sound simple, it takes weeks and weeks of preparation as the slightest imperfection is magnified with the gilt application. Layers of gesso are applied and built up and then sanded down to create a glass smooth surface. Then sizing, which is a glue like varnish, is put over the gesso and allowed to sit for up to 24 hours. In this day and age of immediacy, often quick dry sizing is applied which dries in 2-4 hours. A tiny, thin brush is then used to wisk up the gold leaf as finger prints can damage the finish, and it is layed perfectly over the sizing. Once the entire piece is covered, it is allowed to sit and dry, and then a very delicate brush removes the excess. True gold leaf needs no finish work and it oxidizes to a soft, rich finish.
Unfortunately, most of what is on the market today is either later Dutch metal or gold radiator paint. Dutch metal is infinitely preferable to radiator paint, however, it is inferior to true gold leaf as it has a brassier finish. Though applied much the same way, Dutch metal is not as delicate and therefore, easier to handle and apply and it is not nearly as expensive as true gold leaf.
Too many times what I see on the market is gold paint imitating gold leaf. I see it in flea markets and antique shops; in auctions and in homes and stores. Paint has an iridescence in it that causes it to shimmer in a way that gilt does not. It can be made to appear "softened" and "oxidized", but there are tell-tale signs of paint versus gold leaf. It is duller and darker than true gilt; it does not have the richness and depth of true gilt; and it is often too uniform in application with no signs of the leaf mark. The worst are the fake gold leaf frames on the market where "streaks" are in the background and then they put little "dots" every so often to try and make it look old.
Recognizing true gold leaf from Dutch metal from gold paint takes time. Do not take any dealer's word for it as many do not know. Your best education will come from either a fine painting dealer or a recognized antique frame dealer. You have to touch it and see it in true daylight to learn about it and how to recognize it. My best recommendations for frame viewing are in New York City at Eli Wilner and Lowy & Co.; in Charleston, S.C. at the Charleston Renaissance Gallery; and in Atlanta at Myott Studio Workshop. All are experts in period framing.
Remember: in any antique field, the motto is "Caveat Emptor." In the areas of gold leaf and gilding, be especially cautious as the craft can be so very easily imitated. But like everything in life, once you have seen the best, you will never settle for anything less. Appreciate and enjoy true water gilt.