Gilding on glass
Name: Wenrui Zhao
Date and Time: 9 December 2015, 10:30-13:30
Location: 226 Chandler
Subject:
Making gum water
The essential way to make gum water is to heat mastic together with water. However, I cannot find any specific mentioning of the proportion of how much gum and how much should be mixed together. So the first step of mixing mastic and water is a pure trail and error (and because there is no way of testing how strong the gum water is until you actually apply the water in gliding). Initially I put 4g of gum with 50ml of water, and heat it. Only a few seconds later, the gum started to melt and stick to each other. Based on the size of the gum mass, I felt it might be a bit too little, so I added 4g more mastic.
Then I poured the water out to a smaller container. The gum left in the beaker solidified itself really quickly as soon as the temperature dropped.
Name: Wenrui Zhao
Date and Time: 9 December 2015, 10:30-13:30
Location: 226 Chandler
Subject: Gilding on panel
Before I tried to gild on glass, I decided to practice gilding on panel first to get myself familiar with the properties of gold leaf and the techniques of gilding.
I used a knife to put the gold leaf onto the working station, and cut it into four little squares for practice. The used the brush to pick up the gold leaf to gild it on the panel.
Gold leaf is extremely light and breakable. One needs great care of handling it. I had to find a place in the lab where there was not a great amount of the circulation of air, and sometimes when I spoke or laugh could blow the gold leaf. The author practitioner was clearly of how one's bodily movement might easily affect the gold leaf. In fol 41v, mentioned that one should humidify the gold leaf with one's breath before gilding.
And I used the gum water just created for gilding on panel. The gum water had a strong adhesive quality. As soon as the gold touched the gum water, it would be attracted to the panel. However, the gold leaf was very creased gilded on the panel. One need to burnish it later when it was dried to make it smooth.I tried using both a brush and a burnishing knife to burnish the gold. The knife works better.
Name: Wenrui Zhao
Date and Time: 9 December 2015, 10:30-13:30
Location: 226 Chandler
Subject: Gilding on glass
After practicing on panel, I tried gilding on glass.
The author-practitioner mentioned in fol. 41v, that "silver is twice as strong as gold leaf", so one should use a less strong gum water to gild the silver. I therefore poured half of the gum water I just made into another container, and diluted that part by half for the use of gilding silver.
I found glass as a support for gilding showed a much better effect than wood panel. The gold/ silver leaf could lie much smoother on the glass than on panel. Even though there might be crease at first, the gum water on glass could gradually spread the gold and silver leaf. So when it is dried, the crease was almost invisible, as if it had already been burnished.
And I tried to use silver gum water (the diluted one) to gild gold and gold gum water to gild silver, as well as silver gum water to gild silver and gold gum water to gild gold. It did not show much difference to me. I think the "gum water for silver" itself is an arbitrary concept- because I really don't know how strong that should be, as there is no where to find specific measurement.
Moreover, I noticed that if there is still little crease on the leaf, using a brush to gently burnish would be enough. Using a knife is too strong on a glass surface, the leaf will easily break.
Name: Wenrui Zhao
Date and Time: 10 December 2015, 14:00-17:00
Location: 226 Chandler
Subject: Engrave on glass
I printed out a few simple images for this task. Some of them are directly from the pattern on a reverse painting on glass, some of them are simple wood cuts easy to trace on a glass panel.
According to the recipe, I wetted the paper with a linen cloth. However, the recipe does not specify how wet the paper should be. Moreover, the A4 paper I used is totally different from the paper the author -practitioner would have used back in the early modern time. So this procedure is also based on trial and error.
After wetting the paper, I put it on top of the gilded gold leaf and started to trace the outline of the image. The wetness of the paper indeed affected this process. If the paper is too wet, not only would it stick pieces of gold leaf on it, but the paper would be easily broken, making tracing fine details especially hard. But if the paper is too dry, it would be too tough for the needle to pierce through to leave a mark on the gold leaf.
After leaving a light and thin outline on the metal leaf, I moved out the paper and used the needle to scratch more metal leaf away to make the lines thicker.
The optics of the glass and the metal leaf, and their combination together is clearly an issue worth thinking about. Because the transparency of the glass together with the reflection of the metal leaf means against different background and under different lighting, the engraving would appear totally different effects.
What is most interesting is - as is shown in the last image above, under certain light + background combination , the silver leaf would appear as if it is gold leaf!
(I have problem uploading my video showing better the effect of silver having gold-like effect under different light, will try later)
Name: Wenrui Zhao
Date and Time: 14 December 2015, 12:00-14:00
Location: 226 Chandler
Subject: Making color for painting on glass
The author practitioner mentioned in the recipe that the color to be applied on to the glass pane should be a "turpentine-soaked" color, and to stop it from running on the glass, it can be mixed with "mastic larma" and then heat the mixture before applying it onto the glass pane.
So I made a red lake turpentine varnish by mixing grounded maddar lake and venice turpentine.
And then I heated 4 drops of mastic gum soaked in venice turpentine. It dissolved in seconds under heat.
And then mixed it while hot with the red lake varnish
I then applied the color on the back of the glass pane (the side not gilded) The result is a red color with great translucency and lustre
I also tried to put it against a tin sheet to see the visual effect, as is mentioned in the recipe. The tin sheet indeed "gave color" to the image. The red appeared much more intense and warmer.
(with tin as background)
(without)
