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.

Month-Going Longcase Clock Project Part 5 - Custom Longcase Hands

Cutting longcase clock hands always seems to be a popular subject. Everyone loves to see raw steel turned into beautifully cut curlicues and then turned a beautiful blue-black.

This is one of those "essential skills" that most clockmakers should learn, but that very few do. There are a few reasons for this. Normally it's a time/money issue. Hand cutting and filing steel longcase hands is a time consuming project, and most clockmakers would prefer to buy laser cut or mass produced replacements rather than spend the time and effort on custom hands. It's also expensive for the clients. Who wants to spend 100$ or more on such small parts? Then again, depending on the clock, you wouldn't want precision-cut copies. When you get into rare early pieces, the value of the clock justifies the price for custom work.

For someone like me, I do this work for fun, so I spend whatever amount of time is needed for the work I'm doing (because it's for me). That said, I will happily cut hands for a client so long as I'm adequately compensated for the work.

Anyhow, I think I'm starting to ramble, so on with it.

Materials Needed for Longcase Hands:

- 1/16" thick steel with a carbon content for bluing (test the steel if needed as not all steel will blue nicely) steel must also be annealed for easy cutting
- Paper pattern
- Saw blades*
- Sand paper and polishes

Tools:

- Jeweler's saw
- Files
- Alcohol burner or small torch
- A bluing tray filled with brass shavings, OR a cast iron skilled filled with fine sand, OR a thick brass plate
- Small vise
- Saw support (a wooden plank with a V sawn on the end)

Step 1: Pattern

Choosing the correct pattern is probably going to be the most important, and the most difficult part of the entire process. If you already know the exact pattern that you need, then give yourself a little pat on the back, and count yourself lucky. If you DON'T know which pattern to use, this is where you will have to do your research.

When I last talked at length about clock hands, it was on the mirror clock project, here: http://jcclocks.blogspot.ca/2015/06/mirror-clock-project-part-7-custom-cut.html. All the same points still apply when dealing with longcase clocks. The wrong hands can seriously affect the overall look and feel of the dial and of the clock. Hands for the period I'm copying (1680s, but with more of a 1740s chapter ring) vary WIDELY in style, shape, and size. It's also important to note that certain style hands look better on certain style dials. There is a huge variety of early square brass dials. Some have large ringed winding holes, wide or narrow chapter rings, centre engraving, seconds bits, etc. Everything needs to be taken into account.

It's also partially left to personal taste. I find that a fair number of clock hands are "ugly" or disproportioned in one way or another. The hour hand may be far too large compared to the hour hand, or I find a certain shape too pointy, too ornate, too plain, etc. Anyhow, after probably a month of debating, I narrowed it down to a particular pair of hands that I found on three similar clocks.

John Knibb London, Circa 1685


Joseph Knibb Month Duration Longcase with Roman Striking, Circa 1685


The third clock (not pictured) is another Joseph Knibb ebony longcase, month duration with Roman striking, and also circa 1685. This one was sold in the "Masterpieces From The Time Museum" sale back in 2004. The case is similar to what I want to build (caddy top, 3 finials, ebony case with no trunk door lenticle, but this one has flat Doric hood columns and I want Barley Twist ones).

The pattern was traced freehand on paper based on the dimensions I needed for my dial.



Step 2: Sawing

The rest isn't rocket science. You saw the hands with a jeweler's saw. All the interior openings have to be cut with a pilot hole to start. I find it easiest to start with the openings. Try to stay outside the lines.



Here you can see my cutting support block. The end has a sort of keyhole shaped opening.





I have yet to find a great way to avoid breaking lots of blades. The only advice I can give is to never push against the blade. Let the blade do the work, and turn corners slowly. You can lubricate the blades with wax or oil, but this may ruin your paper template. The blades also become dull from use as you're cutting. *As a general rule, you need 3 teeth for the thickness of material you're cutting. The thinner the material, the more teeth you need. I believe it's 48 teeth per inch for 1/16 thick stock, but I found that slightly finer blades cut a bit more easily. Experiment and see what works. Luckily jeweler's saw blades are very inexpensive. All these broken blades probably cost about 1-2$ for the lot.



Now, no matter how careful you think you're cutting, the results will probably look something like this:



It's not great, but everything else can be cleaned up with files.

Here is the minute hand. Note that I'm using the other end of my saw support block (which has a narrower key slot).



Here are both rough cut hand blanks:



Step 3: Filing

It's hard to explain filing. I think it's pretty self explanatory. Remove bumps, clean up the lines and shapes, thin areas as needed, and then add any necessary "carved" areas such as leaf grooves, decorative ribbing, etc. Use any file size or shape that's convenient. I used maybe a dozen different ones.





I gave them a fairly smooth polish, but I also didn't go too crazy trying to get beautiful perfect edges. I also didn't completely remove some of the steel's texture from the annealing process. I want them to look 200 years old.



Step 4: Bluing

Bluing hands (or other small steel parts) can be a tricky process. The important part is even heat distribution. There are several ways you can blue hands, and some are easier than others. The traditional method is to heat them in a small metal tray filled with brass shavings. This is done over a flame (usually a blue alcohol flame). Alternatively, you can also use a thick piece of brass, and heat the hands slowly (do one at a time). You can also blue hands very slowly in a bed of hot sand. This is how I blued these hands. I used an old cast iron skillet with fine white sand. This method is very slow, but you have the best chance of success.

If you overheat the steel, you will pass blue and go back to straw. If you overheat the tips of the hands, the colour won't be even. If you screw up, just re-polish the whole hand back to bright steel and try again.

The hands are then quenched in oil or water.

If you want more of a black-blue, and you don't want to mess with heat, you can use gun blue. If you have a particularly odd blend of steel that won't blue correctly or evenly, gun blue can also save you. This was the case for a hand I made several years ago.







Apparently I still had not polished the dial plate at this point. I will have to take more photos later.

Month-Going Longcase Clock Project Part 3 - Making a Bell Stand

Part of the restoration of the passing strike components involved replacing the missing bell stand. This is a shaped piece of steel that carries the bell.

Replacements are commercially available, and while they can look okay for certain clocks, the specific design needed for this particular clock means that it needed a custom stand. I prefer to make my own parts whenever possible, because I find that they look a lot nicer than factory made replacements.

Here's a typical mass produced replacement bell stand:



The first step in creating the bell stand is to find a suitable piece of steel, and cutting the blank. I use regular 3/4" x 1/8" steel bar stock from the hardware store. This is fairly mild steel, and it is easy to work with. The blank is cut using a hack saw. This short video shows how I cut the blank.



The rough-cut blank is then further shaped on a bench grinder, or alternatively, with coarse files.











The shape of the bell stand continues to be refined with smoothing files, and then eventually with sandpapers.









To round the stem portion, I begin by coarsely filing the corners, then filing those secondary peaks.









Once the bulk of the shaping has been done with the files, I switch to cloth-backed sanding papers, and I use this technique to round and polish the surface:



With 90% of the shaping and polishing done, I turn to the fitting of the bell stand to the movement. Normally a bell stand has a pointed teardrop shape that sits flat over the backplate, but this one has the style where the end of the tip turns into a locating hole in the plate. To form this hole, the blank is heated, and bent over an anvil.







The bulk of the excess metal is carefully filed away until the profile works with the plate holes. The screw hole will be cut last.



For the top of the stand, where the bell must sit, I use just a cross-shaped design that I came up with. This is a simple design, and it has worked well on the last bells stand I made. Not shown is the threading of the top. It is simply filed roughly into a cylinder, and threaded. A square brass nut is then cut, sanded, and tapped to match.











Here you can see the bell stand fitted to the clock plate.



You can also see the bell hammer, the bell stop piece (attached to the pillar), the hammer cock and a bit of the lifting piece. The hammer spring and spring pin had not yet been fitted.