Thank you to Mary Yaeger @Mary Yaeger for permission to share the very useful gold gilding information in her email to me here:
This is the original text I found on the John Neal Books web site. I've made some revisions in the method I've been using that has worked pretty well, especially with patching small areas. But the last time I gilded was over a year ago, so I apologize as more editing is needed.
With much love,
Mary
from https://www.johnnealbooks.com/downloads/SWatersMylarGilding.htm
Gilding With Clear Film
by Sheila Waters
I've been teaching this method for quite a few years, as it makes handling the leaf easier and makes looseleaf go a lot further, gaining more control of the gold. I have found it a practical method for using my stock of loose gold, making it behave like patent gold in handling. It is well worth the very little time it takes - seconds per leaf. For those without such a stock of leaf, loose gold can be a bit less expensive than patent gold, and the very best, double thickness illuminating gold (loose) is also brighter. Patent gold is called transfer gold in the U.K..
I "attach" loose gold leaf to thin (.002 or .003) sheets of Dura-lar or Mylar. Dura-lar is an archival combination of polyester film and acetate, which I use to protect prints and original art. In the pads of Dura-lar and Mylar, the clear sheets are interleaved with tissue. Mylar is DuPont's brand name for their polyester film product.
I open the book of gold leaf - illuminating quality - and lay a square of the clear film (cut a bit larger than the leaf) with its tissue still on top; the tissue dissipates the static, which, without it, makes the gold jump on to the Dura-lar/Mylar. Then, before removing the tissue and again after removing, I rub from the middle outwards, just as one would paste paper in bookbinding, to eliminate air pockets. Then the leaf should be firmly "stuck" to the clear film, and it can be picked up and strips cut with clean scissors to the size and shape required. I place the newly-backed leaf back into the book.
After breathing on the gesso several times to hydrate it, including on acrylic mediums, I lay the piece of gold with its clear film (that I have cut a bit larger than needed), face down of course! I quickly press on the clear film backing and outline the shape with a hard pencil to make sure the edges adhere. Only the gold that sticks to the gesso ground should leave the Dura-lar/Mylar, so that the remaining gold can be used for smaller shapes, such as dots and for patching. This pressing and outlining is necessary with normal transfer (patent U.S.) gold and also with using loose gold. Leaving out the firm outlining step is most often the cause of gold not sticking cleanly to the outside edges of the shape.
When burnishing, I burnish through another piece of thin Dura-lar or Mylar, as it transfers its shine, and may not have to apply the burnisher directly to the gold. I usually wait a day if I do the latter, to give acrylic gessos time to dry out, then the extra direct burnish will be retained better.
I've never been good at traditional gilding, so I gravitated to "plastic" gessos and experimented with them while still a student at the Royal College of Art in 1951, using a bookbinding adhesive called Spynflex, with my teachers' blessing, while being advised to keep quiet about it! I even used it on a loyal address to the Queen in 1953. I borrowed that address for an exhibition ten years later and was relieved to find it unchanged. I find archival PVA and acrylic mediums work well enough for me, and they don't crack or craze and can be successfully worked with in any part of the US, regardless of temperature and humidity levels. However, I do admire those who achieve great results with the traditional gessos, and using Dura-lar or Mylar as described would help with those techniques too.
Mary's method:
My gold leaf purchased a while ago was single leaf. In the US they don't seem to carry the thinner gold leaf but have "2X," which is thicker and easier to handle (doesn't flake as much).
inked surface is burnished
Note: consider masking out areas if they are not to be gilded. Remember that flakes of gilding come off and adhere to every surface.
Use gum ammoniac from Roberson, available in the US from John Neal Neal Books
How well the gum ammonia works (I figured out that it may not stay gummy enough here in SoCal) depends on climate and other factors. The gum ammoniac also has a shelf life. I found that applying two coats with full seasoning in between each was needed. So I would apply one very thin layer, wait maybe an hour and apply a second very thin layer.
Applying the gold
Cut the gold leaf to size. This is easiest while leaving on DuraLar film as described by Sheila Waters (see below). If you are not worried about being precise I would maybe just use the knife to lift, but there is static and wind from your breath to consider.
Review Sheila Walters instructions before starting; it will help you deal with the static issue. I would add this recommendation: Use the tissue layer to control the static and application of the gold leaf. The tissue on the back of the Mylar breaks the static effect of the gold leaf.
You need to huff/breath on the size to activate it right before you lay the gold on. You use a blow tube; I've been using a wide plastic straw. I find I can tell better if my breath is moist enough.
If you are not using the tissue and Duralar film: float or lay the gold on with the gilder's knife. It should seize onto the activated size. Use a gilders brush or similar: rub on your hair to pick up some static. Use the brush to remove/tidy up the edges, depending on how neat the leaf needs to be in your design.
For getting clean edges: If you are using the Mylar, try my trick of using a tool with a round metal ball point (used for stencil tracing) through the Mylar. It seems to release the static while helping the gold leaf to stay in place.
Burnishing: In my opinion it is best to leave the gold alone for a day before attempting to burnish it. The first burnish is with glassine over the gold. You get a pretty good idea if the gold has bonded well to the size by how much flakes off. But this is a very delicate process. Too much size or too little and it doesn't work well.
Burnisher: Only use the best dog tooth burnisher you can buy. This burnishing is much more careful than burnishing the paper after sizing. Any scratches on the burnisher will scratch the delicate gold leaf surface.
Some people use soap nut to seal the gold leaf. You can also use a spray sealant over your entire painting to protect it. Vaishali said she used an archival product; something, you spray-on.
What can you put on top of water-sized gold leaf?
Shell gold, Sumi ink. Some pigmented water-based paints also adhere. Generally gouache works better than watercolor because it is more opaque.
Additional: Here are notes from the Vaishali Prazmari's Earth class:
Before painting, paint a thin layer of water gold size on the areas you want gold. Either wait until it is tacky (few minutes —depends on your climate) or leave it to dry (can apply the gold the next day if you want). To apply the gold, first open mouth wide and blow from deep in throat to get humid air on the size, which makes it take the gold). To use transfer gold, immediately (after blowing humid air on area) and gently press the gold on top of the area. The gold will appear to cover more area than where the size was placed. Leave and either later in the day or next day, gently brush the gold off of the non-sized areas. Burnish the gold to make it shine.
Often you need to patch or add another layer of leaf. I find that another thin layer of size on top of the previous leaf, and waiting at least 24 hours, works best for repairing.
I also came up with a way to smooth the edges using a
I am most interested in flamelike effects and not a smooth mirror surface. But I prefer to use real, 22kt gold leaf even on very delicate lines, instead of switching to shell gold. But I haven't played around much with shell gold so I don't know yet.