Making Your Own Custom-Tinted Glazing Putty

I recently did an antique window restoration job at work (we're primarily an upholstery shop, but we also do refinishing and occasionally antiques restorations and repairs). Having worked on these antique windows made me want to experiment with mixing my own putty for antique clocks. I've wanted to try making glazing putty for a few years, but I never got around to it until now.

Antique window restoration work:







I generally prefer to leave putty out of a clock once the putty has failed, in favour of installing wooden strips. I believe strips are easier to remove and replace should the glass break again in the future. There are cases, however, where putty is the best option, and gives the best look. Mainly these will be on wooden works clocks from the early 1800s and on clocks up to around 1840.

One of the pitfalls of using modern putty is that the only commonly available glazing putty is either Dap33, or Sarco, which are both plain white. These can be used as-is, and then surface-painted to look old, but the original putty in early American clocks was originally a sort of brick colour throughout (ranging from light brown to a peach or red tone). The goal of trying homemade putty was to see if I could replicate the look of historic putty.

The basic recipe for traditional glazing putty is dead simple. There are only two ingredients: whiting (chalk/limestone dust), and linseed oil.

The exact mixing proportions in the recipes I found are not generally given, because it depends on the amount of putty you want to mix, and the thickness/viscosity of your linseed oil. There is also no specific linseed oil type specified. Double boiled will dry faster, and regular boiled linseed oil will dry more slowly. You could also use refined artist's linseed oil, but that would be needlessly expensive, with little payoff. Some recipes call for a mixture of regular and double boiled linseed oil. It's entirely up to you. Generally, the putty tends to take a long time to dry, so double boiled linseed is is recommended.

For my putty recipe (and keeping in mind that this was mostly an experiment), I used plaster of Paris instead of whiting. Whiting is one of those old fashioned materials that seems to be increasingly difficult to find these days. I've looked for several years and haven't come across any. I could buy some online, but with the price of shipping, it's just too expensive. Plaster of Paris is mainly gypsum dust (calcium sulfate). It is not the same as whiting (which is calcium carbonate), but both are stone dust, and I thought that for my purposes it would work about the same (which it did).



To colour the putty, I decided to use some powdered tempera paints. I came across a large box of these paints at a yard sale many years ago and I had never found a use for them until now. The main colours that I used were red, black, and brown. I also had yellow, and I did use a bit of green at one point to tone down the red. If you can't find tempera paints, you could also try coloured chalk or dry pastels (ground to a fine powder). I believe the putty could also be tinted with artist's oil paints (which are normally made from pigments in a linseed oil base), or with certain types of universal tints, but I have not tried these.



To mix the putty, I recommend using a small dish. Preferably a dish made of glass, ceramic, or metal. I used a small ceramic bowl. The easiest way to mix the putty is to start with a wet mix, and then gradually add more whiting or plaster until you form a stiff dough. I used about 5% tempera paint powders, and roughly 10-20% oil to powder ratio (this is just a very rough estimation). You want to begin mixing your putty with a small spoon or a popsicle stick, and then knead it in your hands towards the end. Knead it very thoroughly.





I was able to mix 3 different colours to do three different clock doors (matching the existing putty colours). I reglazed the dial-glass doors on a C. & L. C. Ives triple decker, and on an E. W. Adams wooden works clock case. I also made patch repairs to missing sections of putty on the lower door of the C. & L. C. Ives clock.

Lower tablet glass from C. & L. C. Ives triple decker clock ca. 1835. The top and left sides were a bit orangy-red while the bottom and right sides were dark brown. Photographed before drying:



Half these areas are original putty, with missing sections filled-in. It's nearly impossible to re-form a perfectly smooth line.



Incorrect modern glass was replaced with wavy glasses in these two dial glass frames from a C. & L. C. Ives, and an E. W. Adams wooden works. The colours were matched to the original putty. One dark brown, and one brownish-red:









The finished results far surpassed my expectations, but there are several additional notes I wanted to mention about the whole process. The first I will mention is the application. If you have worked with commercially prepared glazing putty, you'll see pretty quickly that the home made putty has a completely different texture. Even if you can mix it pretty thick (which I recommend - about the consistency of modeling clay), it will smooth itself into the frame much more smoothly than commercial putty (a bit like icing) and it will appear more glossy at first.

One VERY important thing to consider with this putty is the drying time. You MUST wait for the putty to surface-dry before you attempt to clean any excess putty or smudges on the glass. The fresh putty is extremely soft and easily damaged (like icing), and if you happen to touch the putty when it's only partially dry, it will form a soft oily spot, and it will start to puddle in that weak spot. If this happens, do not attempt to touch the putty any further, and simply set the panel in such a way that the wet spot can lay horizontally to continue drying. The putty in my sample glasses took 2 weeks to dry enough that I could clean the glasses. It's worth the time to just wait and leave the putty to dry. Yes it's slow, and yes it's tempting to want to rush the process, but trying to force the putty to dry more quickly could potentially cause cracking or other problems. A heat gun will also not help dry the putty, because it's the tool that's used to soften and remove old putty. Heat has the effect of further softening dried putty.

You will want to keep in mind that the colour of the wet (freshly mixed) putty will not be exactly the same as when it's dry. It will lighten by one or two shades as it dries. The change is not extremely drastic, but you do want to mix your putty just a bit darker than the final colour you want to match. You also want to start with a bit less pigment than you might think (you can always add more).

The last note I'll share is that once the putty is dry, it can be carefully and lightly sanded (if you have small bumps or screw-ups), and it can also be painted or stained if you need parts of it (or all of it) darkened additionally. I used a glass scraper and a paper towel with denatured alcohol to clean the glass and the extra putty bits (after the two weeks).

Lastly, here are a few pros and cons to making your own custom glazing putty:

Pros:
- Historically accurate
- Inexpensive
- Easy to customize (colour match)
- Beautiful
- Coloured throughout
- All natural and traditional materials
- Looks more professional

Cons:
- Messy
- Slow drying and curing time (2 weeks minimum)
- Tricky to apply smoothly (I used the back edge of a 1" chisel, and there's a bit of a learning curve)
- Excess putty can't easily be stored once it's mixed (discard or find a very tightly sealed plastic container)
- Oily linseed oil rags pose a fire hazard*

* Oily linseed oil rags are a serious fire hazard because linseed oil can heat-up and spontaneously combust as it dries (you can see videos of this happening if you don't believe it), especially if the rags are clumped up. To dispose of the rags, it is suggested to keep them in a container filled with water, OR to lay them flat on a fireproof surface (cement floor/driveway) to fully dry (2 weeks). Alternatively, you can burn them in a fireplace or fire pit.

A Small Project - French Carriage Clock Conversion

This is a small project that I worked on this past week. My client (an antiques restorer and friend) had an old (empty) small French carriage clock case, and he asked me if I could fit a quartz movement into it.



I built a dial base and stand combo from 1/8" Masonite (hardboard) and glued a small section of pine to the base. The stand was painted gloss black, and drilled on the bottom strip for two small screws (which pass through two existing holes in the base). The dial was printed on heavyweight glossy photo paper, and small hands were fitted. The hands are not the best style, but they're all I had on hand.

Overall, I'm very happy with how this turned out. It's a very small clock, so I was lucky that the movement fit in the case. The dial is under 2" and the clock is about 4 1/2" tall without the handle.

Mirror Clock Project Part 3 - Reverse Glass Painting

Picking out a design for the painted glass was a difficult process for me. Because I'm not making an exact copy of any specific clock, I had a lot of freedom for what I could pick for the design. The patterns used on these early clocks range from fairly simple, to extremely complex. Here are some examples of beautiful reverse painted dial glasses in several styles:



Clock 1 is very complex (lots of stencils, shading, and hand "engraving"), and it has the same look as glasses on early Aaron Willard shelf clocks. Glass 2 looks like a well made reproduction of an original pattern, complete with "engraved" gilding work in the corners, and stencil work. I especially like the third lime green Benjamin Morrill glass, with beautiful detailed acanthus leaves, and "engraved" corner flowers. The last 3 glasses use mainly simple stencils, in great combinations of colours. Most of these simple glasses use only two or three stencils.

My first sketch was a pattern loosely based on this tablet (which is unfortunately not very clear).





I simplified the pattern a bit, and coloured it in. I also made some sample colours to see which colour combination I liked best.



Red was the nicest. I liked the colours, but I found that the pattern was a bit too sparse and choppy, so I scrapped it.



It was around this time that I came across this beauty:



The original photo is quite large, and I was able to see all the small details in the tablet. I also ended up finding several variations of this tablet. One is shown below (nearly identical), and I also have one that uses browns, beige, and black, with flower decorations in the corners (the same flowers as the lime green Morrill glass above) rather than the bouquet of leaves. If you look again at the second clock in the first photo above (with the grapes) it uses the same corner leaf design as this tablet.



I thought this pattern looked quite busy, but it eventually grew on me, and I made a new sketch for it. I'm a very visual person, so I always prefer to draw myself a good "preview", especially for a complicated piece like this.





Since this is a copy of a clock from roughly 1820-1830, the glass I'm painting on is salvaged antique window glass. You will be surprised how easy it is to find ample amounts of free antique glass. I often pick up old wooden windows on garbage day, which is a great source of glass. Even if the windows are from a house built in 1920, the glass is usually still wavy, irregular, and often includes bubbles. Modern plate glass only started in roughly 1903, but wavy glass was still available for a long time after this. The house where I grew up was built in the 40s or 50s, and it had some wavy glass in the old original doors. Another source for old glass is an antiques store. One of the local places here in town keeps huge quantities of old window frames, and the owner doesn't keep the old glass. He turns these old windows into mirrors, and if I need any glass, he lets me remove whatever I like for free (as long as I'm careful). Glass shops also often replace old glass (and old mirrors), so if you ask nicely they can probably set some old glass aside for you. My local glass shop will often cut my antique salvaged glass either for free, or for a very nominal fee (1$). Since then, I've bought my own glass cutting tools.

If you plan to do a lot of projects that include glass, I strongly recommend that you NOT buy a cheap 5$ hardware store glass cutting tool. They are simply awful, and you will thank yourself later for spending a little more on a professional cutter. I bought my glass cutting tools from a stained glass shop (out of town). In general, they carry a "cheap" and an "expensive" glass cutting tool. Prices range from around 20$ to 50$ or more, and they also come with different styles of handles (pencil type, pistol grip type, etc). The "cheaper" tool uses a steel wheel, and the expensive one uses a carbide wheel. The "cheaper" tool is what I bought (by the recommendation of the stained glass shop owner), and it should last me for many years of use before the cutter head needs to be replaced. She told me that unless I plan to cut glass on a daily basis, I don't need the expensive carbide version. The tool is made with an internal oil reservoir, but she also told me that none of them at the studio use oil in their glass cutting tools, and to just use it dry. I took her advice, and I haven't had any problems.

Another very useful tool to have for glass cutting is a pair of running pliers. These are slightly curved-jawed pliers with a centre line and rubber protectors. They are used to split the glass in a clean line after you have scored the glass. At 15$, they were a great investment. The only other tool you need for glass cutting is a cork-backed metal ruler. You don't want to use a wooden one unless it's clamped or taped in place, because it WILL slide and mess up your line. Only score the glass ONCE.



Gilding on Glass

Tests were made on scraps of glass to see what method(s) would give the best results for the gilding on glass.



One of the first steps on this glass tablet was to create two thin black rings around the dial opening. This was by far the most difficult and frustrating part of the ENTIRE project. For this I used an old drafting set with an ink attachment. Thinned black paint was used, and after many tries (too thick, too thin, blobs, etc), I got the lines I needed onto the glass. To keep the centre point fixed, I simply used a Popsickle stick held in place with blue tack. My drawing served as my pattern.





The black dots in the corners are references marked on the front of the glass when installed in the door. Sometimes you will see that there is more space on 3 of the 4 sides, so this helps make sure that the pattern is centered on what will be visible when the glass is installed in the opening. The arrow points "up" (top of the tablet).

The next step is to apply the size and gilding. On this tablet, there are 4 "engraved" gilded corner decorations, and a gilded ring around the dial centre.





Once the gilding is dry, the pattern is scraped into the gold, using whatever tools work best for the job. I have seen some people use bamboo skewers, the ends of paint brushes, or metal tools such as small screw drivers. I used a combination of tools. One of them was the bottom of a paint brush, which you can see in the photo:





Add all the necessary details, and then scrape away any unwanted gold around the edges. These look time consuming and difficult, but they only took about 20 minutes each.







These corner decorations don't need to be perfect, or all the same. If you look at the original glass, you will see that they are all slightly different, and some are even crooked, or larger than others.



Stenciling and Painting on Glass

Even if this glass looks very complicated, it actually uses only 4 simple patterns. I drew mine by eye, but you could easily print out a photo and trace them. Once you have your patterns, cut them into stencils. I make my stencils from plastic folders meant for office papers. These are about 1$, and they resist strong chemicals, so they can be cleaned and reused.



The first parts of the design (the parts in the foreground) are done in gold bronzing powders. There is a leaf design at the top and bottom (centre), and the side ovals. Note that my glass is more rectangular than the original, so my oval patterns don't fall partially behind the dial ring. Mine are also less skinny than the originals.



Next, the ovals, leaves, and corner decorations are backed with black paint.



Once these are dry, the next step is to stencil the main leaves. The originals were done in a beige and cream paint, but I chose to do mine with silver bronzing powders instead. In the following photo, you can see a rough pencil sketch of the leaf placement from my drawing, but traced backwards (counter clockwise), so that they end up looking correct from the front (clockwise).

Normally, I prefer symmetry, and I'd like all the leaves to point "up", but ALL of the leaf designs on these early mirror clocks turn in a circular pattern and I have found no exceptions. I have also found that they almost always turn in a clockwise direction, so keep this in mind since you are painting in REVERSE. At this point in the painting process, a mistake usually means that you have to start over completely, since you can only remove things by scraping them off, or with solvents, which both run the risk of ruining nearby details.



Next, more leaves are added in gold bronzing powder. These tend to be random, and plentiful, so don't necessarily rely solely on your pattern. Just place them anywhere that they look good.



Picking the exact shade of reddish orange for the leaves was VERY difficult for me. I wanted something not too dark, not too light, not too bright, and not too boring. It had to closely match the original glass, but I also had to use the paints that I had available. I tried several blends of red, yellow, white, black, grey, brown, and orange, and after over 20 colour samples (only some are shown here), I ended up picking a custom shade of poppy red. The burgundy-brown background colour was actually the easiest to figure out, and that one took only 1 colour mix to get it exactly how I wanted.



Here's a better photo. Part of the problem I was having was that most of the shades of orange either looked too pink, too bright, or too red. You would think that simply adding a touch of black would solve this issue, but adding black turns the colour into a grey or brown. I spent at least a day and a half mixing colours and looking at them in different light.



A lot of these painted glasses are a mix of beautiful crisp details, and really messy, sloppy work. Try to aim for really nice crisp stencil lines (which is hard - a lot of my stencils had to be cleaned up around the edges with the tools I used for the "engraved" corner decorations), and do a slightly sloppier job with your background colours. If your glass is too perfect, it will run the risk of looking too new.



I ran into a problem with my background paint reacting with some of the silver bronzing powder areas. I mention this so that you can avoid it. When I applied the background colour, I thinned the paint slightly with turpentine. I assumed that the turpentine would dry fairly slowly and not cause any reactions, since it's a fairly mild solvent, but I was wrong.





Luckily these areas were fairly small, and I was able to flatten them out slightly once the paint had dried. If the reaction had been worse, I would have had to strip off the glass completely, and start over from scratch.

The background paint needed 2 coats (since it was thinned), and I did not thin the second coat. I'm very happy with the finished glass. You can also see in the next photo how nice and wavy the glass is.

News

I just recently started working on the longcase clock again, as I had other repairs that needed hide glue. So far, I've glued-up, puttied, and painted (touched-up) the swan neck crest for the clock, which you can see partially repaired below.



I also took the time to repair one of two wooden works clocks that were damaged during my move in 2010. This one is a Samuel Terry which I had restored several years ago. All the top pieces are new reproduction pieces that were made to replace the missing originals. They were originally glued-down with hide glue, but they snapped off. I still have to finish painting the reverse glass tablet, but otherwise the clock is about 90% complete, including new tin covers, new square weights, an old bob, and a replaced bone escutcheon and key.



More soon.