In all my years of gilding and in teaching the art, I don’t believe any subject has quite the mystique or confusion as gold size. Whether it’s what to use and when or how to use what and where, misinformation abounds. It generally boils down to what you’ve been originally taught. If you infrequently gild, let’s say some raised letters or a board sign every few months, then you most likely will fall back on past experience and not feel too keen on experimenting. This tends to needlessly perpetuate the old clinched gut and tongue chewing episode that can accompany the process. The adage “If it isn’t broken, don’t fix it” doesn’t apply if you are achieving less than perfect results. Using the correct sizing insures the perfect insecticide for stomach butterflies. Before we begin, remember that only rocket scientists have difficulties understanding the differences in the materials and their uses.

Although I don’t ordinarily specify particular products by name, I will be forced to with a few because of the distinct properties that they contain, In this country, environmentalist gains have unfortunately caused the demise of some traditional manufacturing methods, giving varied results, which is the last thing desired on either a small inscription or a large scale architectural project.

Leaf can be laid into virtually any paintable material depending on its drying time, from seconds to days. Not to say you’ll like the finished product, but to illustrate the fact that somewhere between wet and dry is what we call the tacky stage. The length of this period is referred to as its “open time” or window. This is how “Gold size” differs from the other. Imagine if you will, a side view graph showing a downward incline with the highest point representing WET and the lowest point being DRY. Most paint or varnishes decline gradually whereas a specific sizing will decelerate rapidly to the tacky stage then depending on the type, continues at a slower rate (some, a much slower rate) till it will no longer receive the leaf. The first practiced method for determining when it’s ready, is to lightly rub a clean dry knuckle across the surface listening for a squeaking sound, like on clean glass. It’s referred to as a whistling tack. The French say it sings and a Dutchman will say it toots. The second method is to press your knuckle firmly into the size and pop it back. You should hear a snapping sound with no sensation of wetness.

There are five distinct gold size products we utilize, either alone or mixed for a given use, each with special properties and restrictions.

SLOW SIZE, also known as 12 hour, or the early term “Fat Oil” size. There is a marked distinction between that made in the US (because of the above mentioned manufacturing restrictions) and the always consistent French “Lefranc”. Under normal weather conditions, its initial tack time is about 20 hours (we allow a full day between application and gilding), yet has a safe open time of two weeks. Cold or wet conditions will prolong both stages. Don’t let the extra window scare you. It’s designed for maximum longevity in exterior use and for large scale projects. Once it has reached tack and been leafed it can (in the necessary case of vehicles) be clear coated, outlined/shaded and sent out the door. Just because it gives you the extra time, it doesn’t mean you have to use it. It’s chemically closer to dry than wet so you needn’t be concerned. Besides its open time, it is self-leveling (meaning the brush strokes flow out) and remains elastic. Elasticity is mandatory for brushing out the final gild, as well as flawless pattern burnishing. An example would be the spun or engine turned effect where both the gold and the sizing are manipulated together. I have spun a surface several years old with gorgeous results. Two notes concerning its initial tack, if your gilding experience has been limited to “Quick Size”, there is point where you know without a doubt that it is to far gone, and would be a futile effort to lay any leaf. At this same point using slow size, it would still be six to eight hours away from even being ready. Even though it’s past the wet stage, and will give you a whistle, if by placing an open palm over and lightly touching the surface, you get a sensation of damp cement, leave it alone. A premature gild will first appear fine, yet if brushed up against or velvet burnished will cause an ugly dullness impossible to remove. When correctly tacked and gilded, it will allow you to create one pattern on the surface, and if you wish, lightly brush it out and apply another. One more note, as with any size, apply it as thinly as possible. A grease smudge is not too thin. When the area permits, we often use foam brushes.

QUICK SIZE, also known as 3 hour or synthetic varnish size. Whether domestic or imported, it has always had the same general properties and is unfortunately the most widely taught and used. In use, it must be applied to the surface as evenly as possible as it does not level, or flow out. With matte centers on glass, every brush stroke in its application can show up, explaining why early sign painting instructors used the term “stippled centers”, meaning it had to be stippled out with a short fitch to eliminate the brush strokes. Even this was not widely taught which is evident in some original examples in our shop. Under average weather conditions, its initial set up time is one and half hours with a window of about the same. The catch is, that during its last half hour or so, the elasticity is gone giving you no chance to brush out any wrinkles. As engine turning is the most aggressive surface manipulation, great care must be taken during the available window. Thicker, wet edges will drown and tear out whereas the thinner, non-elastic portions will burn the gold off. Though a competent craftsman is able to avoid these extremes, the air of uncertainty is with him. Here we address the prime use of quick size, which is to speed up the initial setting of slow size. Our favorite mixture is a 50/50 ratio. It will be safely ready overnight or about 8 hours. When set, the window is extended to a week or more. Even the addition of 25% slow with 75% quick gives you an available 8 to 10 hours open time with about a 4 hour setup. With all of the softness eliminated, burling with a drill motor is worry free. I might add that the final gild achieved with the slow size addition is that of golden velvet.

Realistically, logistics and deadlines are the pressing issues, which brings us to another product new to the market within the last few years:

1-SHOT FAST DRY GOLD SIZE. This has become our favorite for time constrained, same day work, whether raised letters or mattes in a window job. Although there are inherent skinning problems while in the can, it contains the best of both worlds. Tack-up time can be as little as 45 minutes to an hour with four to five hours open time not uncommon. It is self leveling like slow size and remains very elastic to the point where it no longer takes the leaf. I generally gild at an hour and a half, giving a flawless velvety effect. If a longer window is desired, you’ll find it also compatible with slow size. The skinning problem can be avoided by storing the can upside down and the lumps reduced by not stirring or shaking.

The above solvent based sizings are best colored with universal tints, found at your local paint store. These come in a range of colors and are compatible with oil, water and lacquer based paints. Being essentially wet pigments they don’t contain driers or retardants, which as in the use of lettering enamels can effect the proper setting of the size. You can add up to 10% of the tint safely. A small amount of color allows you to see where you’ve been and should be in contrast to the background its being applied on. Yellow is the most common with red a close second. Sizing over a very dark background requires additional color or undercoating with a lighter base to eliminate visible undershadowing through the leaf. Another nemesis we’ve solved are the seemingly unavoidable specks of stuff that gets onto a sized smooth surface regardless of your dust precautions. I’m convinced these particles are inherent in the packaged materials, and commonly used straining methods don’t eliminate them. By warming up the size, tinted or not, in a microwave oven, or carefully on a hot plate, the contaminate are easily removed by pouring the material through a paper coffee filter.

To this point, the objects to be sized have been broad surfaces, as in flat lettering and ornamentation, or in three dimensional objects. The intended application being as even and consistent as possible. With the current resurgence of period style signage or shall we say, a return to elegance, another snapping dog has surfaced. Gilded fine line striping is a design element as important to vehicle decoration as it is to restoring an antique safe. When a broad line of 3/8” or wider is applied, it will appear undressed, without a thin color line running parallel to its edges. This is undisputed, though their use is explained as hiding ragged edges. These are not appropriate for thinner lines and requires a forgotten formula and a little understanding to solve. Envision, if you will, the flow of size from a sword stripper as an elongated drop. If viewed on end, it is thicker in the middle than at the edges. The use of quick size forces a choice between patchy edges or a drowned center, neither of which is acceptable. The manufactured nature of slow size to level out will give a bled appearance when gilded. Again unacceptable. Acquire a tube of high quality cadmium yellow artists oil paint. Squeeze off and discard any separated oil and mix into a jar with an equal amount of gold size. A mix of 50% color, 25% quick size and 25% slow size will take 12 to 14 hours to setup. The pigment acts as a filler, giving it body as does the addition of gravel to cement in making concrete. The result is an evenly tacked up stripe that gilds without blemish and can be timed to your preference.

We occasionally produce short runs of gilded decalcomania transfers which require the sizing to be silk-screened. We use an air dry textile screen ink by Nazdar (PX-32 gold, permaflex) with a 30% addition of slow size for open time. As always, have a test patch or piece to check the tack, but normally you can safely gild after several hours.

The final two products of importance are water based. WUNDA SIZE, commonly referred to as gilder’s milk, is restricted to interior use and has a poor leveling quality, but is unparalleled for tack aggressiveness when using the heavier metal leaves (brass, copper & aluminum). It is milky when applied and is ready to leaf when it turns clear (15 to 20 minutes). Described open time is 24 to 30 hours but days are more realistic. It is invaluable when reverse gilding deep carved glass as oil/varnish based sizes are amber in color and result in a dirty appearance when using white gold or aluminum.

Last but not least is INSTACOLL. It comes in two parts, your choice of a clear or yellow base coat, and a clear activator. Primarily for three dimensional objects, it creates an unbelievable electroplated shine for interior or exterior use. After the base coat has fully dried (3 to 4 hours), a quick setting milky activator is applied. Within 10 minutes, or when clear, firmly press on patent gold to the surface. When fully leafed, polish with velvet. Its open time is a good hour or longer and can be reactivated as necessary. For special effects it can be engine turned with a drill motor.

I’d like to finally share a few shop practices to keep the art trouble free. In preparation for sizing on dry, slick surfaces, we wipe over the area with pharmaceutical grade kaolin (shadow kaolin) to prevent any unwanted leaf from sticking to the background, and to avoid holidays when applying the size. It clings to the surface and doesn’t contain any visible particles to contaminate the size.

After the leaf has been laid, we use a clean, short-nap paint roller to firmly press out any air bubbles before brushing off the excess gold. This applies to painted surfaces as well as glass work.

With selective gilding on painted surfaces, no matter how careful we are to protect the background, there is often a piece or two of leaf stuck to the surface. Assuming the background was sufficiently dry, the slickness of a high gloss paint can attract and trap a piece of gold giving a mirror-like shine. If these are noticed within a few hours of application, they can be removed easily by wiping over the area with a cloth or soft paper towel saturated with a concentrated vinyl application fluid (SPLASH) or a degreaser such as SIMPLE GREEN. These surfactants break the leaf’s surface tension and allows it to be wiped away. Only those areas of leaf not attached to the sizing will be removed so it’s safe to wipe over the whole inscription. If the shiners are left on the surface beyond a few hours, they can become extremely stubborn. When this happens, we mix a little water with our 3 micron alumina polishing powder into a paste and gently wipe away the spots. Its micro fine abrasive will not dull the background but would obviously damage your unprotected lettering if touched.

Warning: Never clear coat any surface applied gold leaf unless you are assured that it will be destroyed if not done. It is considered a necessary evil for vehicles or other heavily maintained surfaces and at best, will shorten its natural life span. As for our choice when it is necessary, we’ll leave it at Frog Juice for the time being.

A few sidebar items; Ancient Egyptians were known to have used blood as sizing. In the 15th century, the respected Cennino Cennini recommended using a glair made of egg white to adhere the gold to glass panels. When dry, a design would be etched in and the excess gold scraped away with a wooden stylus. For today’s food fashions, try a little honey water as the size for gilding that special slice of chocolate cake. You just can’t beat natural materials.

(Thanks to John Jordan for supplying this document to this site, and also to Kimberly Zanetti for retyping the old document for use here!)