Cementing, cleaning and polishing a stained-glass window

Part 1: How it all happened in one particular studio

In the studio where I learned, one man drew the design, another cut the glass, a third man painted it, a fourth assembled the glass in lead and did the soldering, while a fifth cemented the finished window, picked it clean and polished it.

stained-glass cement

This fifth was really just a boy who’d left school early and unqualified.

The owner paid him less than anyone else, having calculated the lad would struggle to find a job elsewhere.

If you are romantically inclined, you might suppose the other staff would show compassion and try to bring him on so he might better his position in life.

But the boy was daily mocked.

Therefore he soon harboured such resentment and was filled with such aggression, he was not trusted on the studio floor, but was confined to a small, filthy, ill-lit room at the back of the studio – the “cement-shop” – where he did his thankless work from 8 o’clock till 4.

Cementing – thankless work?

Yes, thankless, though the job he did was vital:

  1. If the windows are badly cemented, they will let in water.
  2. If the cement isn’t scrupulously cleaned off, the windows will look messy.
  3. If the leads aren’t polished till they gleam, the glass won’t look its best.

But only a handful of the workforce saw things like this.

Cementing – worrying and demoralising. (But it should not be like that)

As an apprentice, I was sometimes ordered to the cement-shop to lend a hand.

It was hot, exhausting work throughout.

Perhaps the most important part of the job is this:

You must take great care to push the cement underneath the flap of the lead in sufficient quantity and with enough (but not too much) force that it meets the cement you push through from the other side.

It’s crucial that the “2” cements are pushed until they meet. Then, somewhere very near the heart of the lead, the cement will set together.

Now, if it at all matters to you that windows don’t leak, you will worry greatly about this, and often wish it were possible to devise a fool-proof method (short of X-Rays) which guarantee success.

You will also worry that you are at the end of a long and skilful process – designing, cutting, painting; and how completely awful it would be to break a piece of painted glass right now, just as the studio is gearing up for shipment.

Whiting for stained-glass cement

You often worry that you might break a piece just now …

It is also demoralising work throughout.

The reason?

You are busy when everyone else is idle and triumphant, because their work is done.

But you cannot even enjoy those times when your own work is slack, because you will immediately find yourself the object of other people’s ill-feeling (since they now have a lot of work to do, and the owner knows that you are waiting, which costs him money, however little, which makes him angry).

When you are your own masters, you can choose to do things differently and better

Here at Williams & Byrne, we’ve spent the greatest part of last week cementing, cleaning and polishing a set of windows, the first piece of whose glass David cut eight months ago.

Four lancets. Each one just over a half-metre wide and two metres high. Each one in 4 cuts.

If this menial, filthy job were best-served by hiring someone else to do it, we would always find the necessary money to get it done that way.

Stained-glass windows: cemented and drying

But it is not best-served like that.

It is less worry when we do it ourselves.

In this country, I can scarcely believe it’s practical to delegate a job like this and not expect there to be some breakages or leaks or unclean glass or improperly polished lead or something just gone wrong which no one spotted because they don’t take it sufficiently to heart.

So, since we wanted this last stage to go smoothly, we cemented everything ourselves.

Not quite everything – we brought in extra (over-qualified) help

Just one concession: for the leading, we’d hired an extra pair of hands.

When the leading was finished, our hired help then knew the windows well enough (even though he hadn’t had a hand in painting them) to remain with us last week and help us with cementing.

Polishing the leads

Hard-nosed business is also good for windows which don’t leak: here’s how

Three hard-nosed points concerning business now.

  1. Naturally, since cementing really is that important, our hired help was paid the same fair rate throughout: he wasn’t paid less for the days he joined us with cementing.
  2. If the day ever comes when we employ permanent staff here, everyone will need to do whatever work is best for the project. If this means painters getting dirty with cement, that’s just how it’ll have to be. (It’s how it is right now.)
  3. No way will cementing ever be delegated to anyone unless they are over-qualified, because over-qualification is often the best guarantor of success with this particular job.

That’s all for today.

Next time:

  1. Off-the-shelf cement vs. make-your-own.
  2. When to do things the old-fashioned way vs. using modern gadgets.
  3. Tools for cleaning cement. (Do you own a dental pick?)
  4. The kind of brush we use to burnish and polish our lead so it gleams like gun-metal.
Polished stained-glass leads

Polished leads

So, over to you now: Do you have a recipe for home-made cement?

If so, please use the comments box below to share.

Also: we’ll all be grateful for any instructive anecdotes or tips you have about cementing in particular or learning and apprenticeships in general.

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47 thoughts on “Cementing, cleaning and polishing a stained-glass window

  1. When cementing, I liken it to finishing off the hull of a wooden boat, which has thousands of screw heads to bung so they are waterproof. Each has a plug of wood that is dipped shellac, inserted in the countersink and, when dried, cut off with a sharp chisel. Renowned wooden boat builder Bud MacIntosh said in his book on the subject that there was a little integrity in each bunged screw. That thought keeps my tired hands going when brushing and brushing and rubbing and rubbing.

  2. Much of my cementing is on repaired old panels, and it is unbelievable how much strength new cement adds to an old window. It also leaves a lovely patina. According to Geoffrey Wallace the new linseed oil rebonds with the old particulate material, not unlike repointing stone walls. I believe this is true.

    Recipe: 2 parts whiting, 1 part plaster of paris, boiled linseed oil to make “batter”. Also thin with turpentine as an evaporant; and lamp black to give a grey (blending with the leads).

    Old windows with lots or some cement remaining (merely vacuum to get out loose stuff) get a somewhat wetter mixture for better penetration and bonding. Mix and dilute or thicken till it “looks right”.

    One thing I’ve always done is: after scrubbing the cement under all the flanges I sprinkle on dry whiting rub it all over just with gloved hand, then pick all leads with a sharpened stick. Then I sprinkle on a bit more whiting and spread it around til it covers the wet edge of the cement against the came flange. Now I dry brush – actually with the same old scrub brush I’ve used for 20 years. Then remove excess whiting dust and semi-dried cement, and pick the leads with wood stick, this time with shop-vac in hand.

    I usually take one side to this point, then turn and do the other. Even on new work, this seems to minimize squeeze out on other side.

    My polishing is done with one of those red mechanics rags – rough enough to remove cement from leads and give everything as nice sheen.

    • Very useful to know your recipe: we’ll post ours next time.

      Interesting what you say about how new linseed oil rebonds with old particulate material. When I was working in the studio, we often had vast quantities of 19th century windows requiring new borders (so as to make them fit new openings). And so we had to scrape down and clean the old lead so that, with new lead (and new glass) abutting it, everything could be neatly soldered. And what I found was: it helped to wipe the old lead first with oil, before scraping it clean. It seemed to me the old lead actually absorbed it. And this fits in with what you say.

      • Stephen, today I cut down an old window to fit a new opening, 1/2 ” flat H copper border for strength to hang in a space. I took a flux brush and wiped all the old cut ends with Boiled linseed. Hum! It did seem to refresh the metal, certainly made scraping easier to see, and seemed to take the solder more easily at the end. Thinking now before I cement it, I’m going to wipe all the leads with linseed, and see how that goes! Nice tip, thanks, Geoff C.

        • Interesting idea about wiping the leads with oil: I’d love to know how that goes. Now this is possibly related: to help burnish our leads (after cementing and cleaning), we sometimes rub tallow across our brushes – made from jute – before we start.

  3. A much awaited subject that conjures up tales of kneading metal casement putty with chalk/white spirit to the required consistency, and darkening accordingly with Zebrite.

    For 2 years I cemented windows, and due to an overzealous and often sore thumb, I learned my repair skills before I had even made a window.

    This critical process really is the final stage that will provide strength to the lead matrix, waterproofing, its patina and finish: this is the most important stage of the whole beautiful process, it really is a big deal, it has to be waterproof, and beautiful: no pressure there then! Also make the glass gleam and the lead shine – a big subject.

    Thanks for continuing to inspire me,
    Graeme

  4. Hi Stephen,
    Yes, cementing is a bit of a fag, but I’ve always thought of it as an almost magical process that transforms a fairly raw looking and certainly unstable object into an impressive work of art.

  5. The setup time frustrated me with off-the-shelf putty, so I’ve been making my own for several years.

    Until recently, the liquid was 1/2 boiled linseed oil 1/2 paint thinner, but California stopped selling paint thinner a year or so ago. We tried mineral spirits, but windows were oozing for weeks. Now we use turpentine. So that’s 1/2 oil, 1/2 turps.

    Mix it well before adding fresh Plaster of Paris (check package for expiration date). Mix to desired consistency. Add black powdered cement coloring (the liquid does not work) to the shade of gray you want.

    I always leave a float of the liquid when setting it aside in a closed container.

    You can add liquid if it starts to set up, or more powder if it’s too runny.

    But always be sure you stir the liquid so you don’t have a float of oil off the top.

    This works for us, but I am very interested in the recipes of other makers.

    We burnish with a brush attachment on a drill.

    BTW, once one of my sons was doing the putty work for me and didn’t let me know he was out of the oil so he just used the paint thinner. A few months later, we had to deal, at great expense with leaky windows. I guess it’s a chemical reaction.

    Thanks for taking on this important phase of making windows and opening it up for discussion.

    Best,
    Mary Ann Celinder

    • Thanks for your recipe, Mary Ann: I’ll gather them all up and put them on a single page for everyone.

      Useful – though painful – story about the leaky windows. I have one too. So does David. It certainly focusses one’s attention.

  6. I always make my own cement-didn’t know you could buy it. It appears to be entirely watertight: on gale-torn rainy nights, I used to worry about windows I’d done for a friend, but seven years on, they are still watertight.

    I empty out a small tub of linseed oil putty, bought fresh from a local glaziers – I always ask the lad if it is fresh: they have such a turnover there, I have never bought a dud tub yet.

    I scoop it out, and knead it well, then put it on a large plastic tray and sprinkle it with black powder paint (the sort that children use).

    I add small amounts of white spirit, and chop and knead, chop and knead until the putty is sufficiently soft and black to be able to “flick-push'” the putty under the cames with a stiffish toothbrush.

    Twice, I have had a piece break, and it is a dreadful sound … like expensive chocolate snapping. Each time it has happened because of not concentrating, and slipping off the came when pressing down the cames.

    The tutor when we were learning used to say, “Don’t use too much whiting: you are not baking a cake.”

    I use bamboo skewers to clean up, then a bristle ‘scrubbing’ brush, then, over the days, go around the glass/ leads margin with an etching needle while the putty is still soft enough to remove easily.

    Soft bristle brushes and a little zebrite make the leads gleam, and polish the glass too.

    Fresh eyes are good, to see lurkers – sneaky bits of microscopic putty that adhere to the cames.

    I’ve not read other’s comments yet, so they may do things entirely differently. If there are better ways, I’d like to hear them.

    Cementing is crucial, as the weather in the UK is rainy and wet, and people expect their doors and windows to be rainproof.

    • We too buy in linseed oil putty, though mainly when we’re puttying by hand: i.e. not using a brush. This is because the putty is fairly close to the consistency we actually need. (Whiting to thicken it; or boiled linseed oil to thin it.)

      Zebrite: can you still get it? And does it still contain lead? Myself, I tried a modern lead-free version and it was useless. So I came to the conclusion that, to blacken the leads, yes, cement black (for instance) rubs out from the putty and plays a part. But the main role is actually a chemical one: rubbing lead – just the act of rubbing it – will blacken it. (Though you do need to put a lot of energy in!)

      • Dear Stephen,

        I think people tend to stick with how they were first taught, and the tutors used to use the mix above, and called it “making your own” which, after reading this information, isn’t quite true … It is like saying “I make my own ‘Eton Mess’, but I buy the meringue and frozen raspberries from Waitrose”.

        Zebrite, as a brand: I think it has died as a brand, but there are still grate polish makers, but I still call it “Zebrite”. It actually contains powdered graphite, and it is the graphite which makes the gleam – a bit like we say “lead pencil”.

        Your mention of the Apprentice who was stuck with the miserable task of endlessly cementing: my own son did an ‘Apprenticeship’, and it was very frustrating – some workplaces expected him to be a minion, to endlessly clean, and to go and buy sandwiches. He soon left these places, and found a better place where he could practice the finer parts of the trade.

        As years passed, and new Apprentices were brought in, he did take the ‘prentices under his wing – if they showed keenness and aptitude. But in too many places, the ‘prentice is the bottom of the pile – and yet it is they who make the oak pegs that hold the beautifully cut joints of oak buildings together. The equivalent of “cementing” in your post?

        • Hi Catherine!

          Myself, I firmly believe that buying-in-and-adapting is an important approach: I am very glad you brought it up, because that allowed me to mention how we indeed buy-in-and-adapt and use it for those situations where we believe that pushing with a brush is not what we want to do.

          Thanks for the news about “Zebrite” or whatever it’s now called: some kind of stove blackener which still contains graphite.

          I am glad your son emerged well from his experiences. (It can indeed teach us not just technical skill but also compassion.)

          Best,
          Stephen

  7. Like Geoffrey, I too have adopted much of my technique and formula from Geoffrey Wallace and use the same recipe. It is remarkable how an old thirsty window will absorb a thin mix of cement and practically regenerate itself to new condition.

    I believe what many of you refer to as “mineral turpentine” is known to us in the US as “mineral spirits”. I had used “pure gum turpentine” for years with great success but for the last few have preferred mineral spirits for its low odor and safer characteristics.

    For new panels, we grout both sides and dust with a small amount of whiting. At the end of the day we pick the top side (typically the painted or textured side) with an old screwdriver ground to a point, vacuum and brush with palmyra bristled brush. The next morning the panels are usually ready to be flipped and cleaned up on the bottom side. Final polish with tampico bristled brush after cement is well-cured and panels are ready for bars or wires. Adjust the cure time and consistency of the mix based on temperature and humidity.

    It would seem that a fresh batch of cement performs much better than a pail that’s sat around for a few weeks … Does anyone bother mixing their cement fresh each time or, like me, stir up half a pail or so and use it until it’s gone?

    • Very important point you bring out: adjust the cure time / consistency of the mix, based on temperature and humidity.

      This window we’ve just cemented had a lot of plating in it. The plated glass we copper-foiled beforehand to minimise the possibility that cement might seep in and mushroom between the separate bits. But, the fit now being tight, this was another factor in choosing the right consistency of paint.

      Your last question: if it’s revivable, we’ll re-use it. But the pace of our studio is it’s only a few times a year we get cementing – and (confession here) we usually don’t remember to keep turning the half-used cement pots every fortnight or so. In other words, it’s generally not revivable …

    • I use the same batch till it’s gone, and it’s homemade by a studio I used to work for. I do try to keep a skim of oil on top, and add more turps or oil as needed and rework it. Haven’t gotten any returned pieces …

      I guess the brushes I use must be tampico; straw-like. In a pinch I’ll apply the putty with my fingers: sometimes I’ll have a really old piece to repair, with minimal replacement lead or glass or worse yet, with zinc they don’t want replaced, just re-soldered …ugh! … So there may be gaps I have to fill by hand or brush very delicately. And sometimes to apply the putty I’ll use a tossable nail-brush.

      • “Straw-like”: yes, ours too: jute. They’re a bit bristly to start with, but a colleague suggested rubbing tallow into them when new to soften them, and this works marvels.

        Great suggestion to use a nail-brush, especially with small or fragile panels.

      • I needed to solder some oxidized zinc and remembered a way to get a good joint. The first studio I worked for only used zinc and used muratic acid as a flux. Nasty fumes, but you’ll get a better bond than just steel brushing.

  8. Had an interesting conversation with some lads from research and development that worked for a company that manufactured commercial putties and other such products. One of the products was a “cementing” compound for stained glass windows.

    I was working in a studio that was using the commercial product and it was not behaving “normally”. (I make my own cement with the same formula that you use.) I called the company and asked to speak to the folks that worked in shop.

    Upshot of the confessional conversation was that they used soya bean oil instead of linseed oil due to cost factors. It seems that soya bean oil has a polymerization life of 20 years where linseed oil can take 75 to 100 years depending on the environment.

    Explains those 1995 panels that walk into my studio looking like sagged drapery.

    • Gerry, That is alarming. Seems things are now made with built in obsolescence. Cement is something we place our trust in, and I assume, like you, that an average window will last almost a century without the need for recementing. It would be mortifying to get one back because it had sagged like a leaden curtain.

    • Soya bean oil vs. linseed oil: a magnificent demonstration of why it’s often best to keep things simple i.e. make your own. (This time we didn’t. So I hope the soya bean oil phase has finished.)

  9. Even though most of our work here is for domestic applications, now and then we receive a really lovely mandate for restoration or (happy day) a total new chapel window or two. My cement recipe is:

    1 CUP OF WHITING, 1 CUP PLASTER OF PARIS, 1.5 CUPS BLACK OXIDE, BOILED LINSEED OIL, ABOUT 125ml OR MORE IF NECESSARY, NORMAL TURPENTINE.

    FOR BRUSHING IN, 3/4 PLASTER OF PARIS, 1/4 WHITING.

    Work into lead lines with soft brush. Follow this by “painting” the lead joins with a mixture of 90% stove black & 10% water, making sure that the glass is cleaned before this mixture dries.

    Allow to rest for 24 hours then polish up as usual.

    I have found that polishing up can be expedited by cutting a small round section out of a soft flat brush (one of those oval horse brushes works well), drilling a hole in the centre of the wooden part an fixing it to the end of a drill. This works like a bomb and reduces your elbow grease time significantly, and leaves a beautiful sheen.

    • Barbara – One of the tools you see in a lot of the studios here are old floor polishers with the old bristle brush heads. They turn up in Salvation Army Thrift Stores cheap, cheap, cheap. Remove the long handle and reconfigure the off/on switch. Some can be found with the snap-on buffing pads. We use a car polish buffing unit for final cleanup. Gerry

  10. I have been making putty for about 15 years. After studying and collecting dozens of recipes, this is what I use:

      Linseed oil; boiled and raw 49.5% each

      Tall oil 1% (helps in the mixing of oil and powder)

      Whiting: 3 parts 25 microns, 1 part 3 micron

      Talc 1/2 part (use enough to reduce stickiness)

      Black concrete color (amount to suit)

    I have a small Hobart restaurant grade mixer with a bread hook attachment. Put oil in mixer bowl and slowly add the powder.

    I use my fingers to putty. So this recipe is for a soft “taffy” like consistency

    Vic

    P.S. Well, I posted you comments without seeing/reading the other posts.

      – First off, I consider Geoffrey Wallace as a friend and someone that I respect. However I do disagree with his putty formula as a general putty. His premise for adding plaster of Paris and mineral spirits has to do with in situ reputtying in future years. Plaster is hygroscopic so it will absorb liquids i.e. oil and moisture. If you reputty the new oil will soak into the old putty. But moisture just might get absorbed before you get to re-putty. Moisture is not a good thing under the leads. So I think the use of plaster of Paris is a gamble.

      – I also feel that the use of any solvent in the putty mix will short the overall life of the putty.

      – The drying time of raw linseed oil takes forever. That is why I mix it with boiled linseed oil.

      – And lastly the use of lamp black: it is not as color fast as concrete color.

    Vic

    • Really useful points you make. Thank you for clarifying the distinction between raw and boiled linseed oil (I was going to ask!). Also for bringing it out that Plaster of Paris is hygroscopic: thus your preference for whiting.

    • Vic, I like your recipe. But I’m confused with the Whiting part.. Is is 3 parts parts or 1 part . and what is a micron? Sorry for my ignorance.

      • Question:
        “I have been making putty for about 15 years. After studying and collecting dozens of recipes, this is what I use: Linseed oil; boiled and raw 49.5% each Tall oil 1% (helps in the mixing of oil and powder) Whiting: 3 parts 25 microns, 1 part 3 micron Talc 1/2 part (use enough to reduce […]

        Vic, I like your recipe. But I’m confused with the Whiting part.. Is is 3 parts parts or 1 part . and what is a micron? Sorry for my ignorance.”
        Answer:
        A micron is a unit of measurement. “Whiting” or the technical name of “calcium carbonate” is manufactured in different granular sizes. From course to very fine. 25 microns is “larger” then 3 microns. Think of this as a bag filled with large marbles. Because these are round there are holes where the edges touch. If you had enough small marbles to mix in, you can fill these holes. That is why you use to sizes of whiting to get a better mix. The parts refer to this mix. 3 parts of the large whiting (25 microns) to 1 part small whiting (3 microns). When I make putty, I make about 3 gallons at a time. To do this I use fill a one pound coffee can 3 times with 25 micron whiting and 1 time with 3 micron whiting, thus 3 parts to 1 part.

  11. When doing the final polishing to the glass and came, I borrowed a idea from my re-leading bench.

    When polishing shell casings in a tumbler, a small amount of linseed oil is added to the corn cob medium and the brass casings always come out bright as new.

    So, after the putty has been forced between the glass and came, the corn cob and linseed oil mixture is sprinkled on the glass and came. Then, a stiff bristle brush “like the one in the picture” is used to brush vigorously over the glass and lead.

    The glass comes to a very high polish and the lead is left with a deep patina and high shine. The corn cob cleans the excess putty, leaving less final cleaning with a bamboo stick.

      • Stephen,

        Please forgive any misspelling: I thought I’d used the word reloading not re-leading. Reloading is the process of recharging rifle or pistol ammunition. This process requires the polishing of the empty brass shell casings using a vibrating or rotating tumbler filled with empty shell casings, ground corn cob medium, and boiled linseed oil.

        The ground corn cob can be purchased through any gun reloading supply company.

        Only a small amount of boiled linseed (not raw, it doesn’t dry as fast) oil, maybe one (1) tablespoon to one (1) pint of medium is needed.

        This has a two-fold purpose: to keep dust down, and as a polishing agent.

        The corn cob is absorbent and also with the brushing it helps to pack and clean the putty at the came edge.

        I have also used plain saw-dust, but this some times leaves small slivers and fine chips in the putty which require further cleaning and the more brushing to repair the dent from the chips.

        Ground Walnut shells are also available for the same polishing purpose but I’ve not tried this because I didn’t think it would be as absorbent as the corn cob.

        My reason for trying corn cob and sawdust was the question: “What was available in the 11th and 12th century?” I hope this helps.

  12. I have been doing glass since the early 1980s. Started working in studios doing leaded glass in the late 80s. One shop used premade Dap (ugh), and the other made their own (I need to ask for the recipe).

    We did pieces start-to-finish, except the drawing, and only once did we have Albinus Elskus come in to paint.

    I finally learned 3 years ago, but the new, never-used kiln I have doesn’t have a manual. No luck finding one yet either. But that’s beside the point. When I was hired at the 2nd studio (where I actually had learned to do glass), I was started at minimum wage till he saw that I had learned well the few years I had worked at the other studio. Then I got a nice raise. Even though I had been constructing on a second cartoon, they accomodated me. Then one day, we had a face-off, the owner and I making identical patterns using our different techniques. We were neck and neck, lol!

    But at both studios, everyone did everything. And it was so nice to see the final burnished project.

    Putty, then brush in whiting, then sawdust overall, and a final burnishing with the natural bristle brush. The smell of turps, whether puttying or oil painting has always drawn me in.

  13. Hello Stephen, Very interesting to read about your cementing and all the feedback comments.

    I was taught a great deal by a master glazier who had served his apprenticeship with a stained glass firm in Dublin and latterly worked for Goddard and Gibbs in London. He used to make cement in vast quantities. I don’t have a precise recipe, but it all started with a very large bucket:

    • Add sufficient whiting for the quantity of cement required;
    • With care, add sufficient boiled linseed oil, stirring to reach the required consistency;
    • For blacking the mix, add a squirt from a tube of artist’s ‘lamp black’ oil paint.

    He never used Plaster of Paris, but sometimes – to help speed up the drying time – he added a small quantity of Terebine Liquid Driers.

    Zebrite was sometime used for final polishing, but with great caution: it can be messy stuff especially with open, seedy glass.

    Modern alternative is Stovax (Black grate polish) which contains graphite.

    I use a selection of brushes, hard and soft, for final polishing.

    • Thank you for the timely reminder about the necessary care to take with seedy glass. I certainly remember using a needle to clean up broken dirty seeds, one-by-one.

  14. I found this topic really informative and it answered a lot of questions I’ve always had about cementing too.

    When I’m cementing a panel, my partner, who is a woodworker, always comments: “Is it supposed to take that long??? Surely it’s not commercially viable to spend so much time doing that!!! Isn’t there some power tool you could use to make it quicker???”

    I actually enjoy the cementing process and find the process of cleaning the cement from the lead quite therapeutic. And I love the final stage of polishing the lead and glass to really bring the finished piece to life.

    When my partner chastises me about how long it takes I often worry that maybe I am being slightly anal and too much of a perfectionist but reading your comments has totally reassured me, and of course I made him read it all too, which was most satisfying, so thanks very much – I don’t think he’ll be nagging me next time I’m cementing!

    Also, I have always wondered if the cement they sell in the stained glass suppliers shop is better than the cement I was taught to make at college and reading this has reassured me about that too. Which is good as the stuff they sell in the stained glass suppliers is a lot more expensive too.

    I use a standard glazing putty, mixed with black powder paint and white spirits, mixed to a thick custard consistency so you can brush it right under the lead but also brush a lot of the excess off the lead too.

    Over the next few days as it dries I clean up with a wooden stick, which my partner makes specially for me – he does have his uses, despite the nagging!

    At the start of the process while the cement is still quite wet it’s easy to remove from the lead and as it firms up you can push it right under the lead and get a nice neat edge with the stick. (Obviously you have to keep an eye on any putty seeping through to the other side and making a mess on the lead.)

    When the putty is firm enough not to squidge out I turn over the panel and repeat on the other side. I’ve never used whiting as it wasn’t something we were taught at college but I am curious whether other makers think it makes a significant difference to aiding the process?

    Thanks for sharing your experience and knowledge!

    • One thing about off-the-shelf (as Gerry Eversole makes wonderfully clear) is: what happens if someone from the accounts’ department decides to reduce costs by adjusting the recipe e.g. replacing linseed oil with soya bean oil?

      Like you, we’ve mainly used standard glazing putty when “buying in”: adjusting it and colouring it ourselves.

      Also like you, we’ve fastidious about a nice neat edge: can’t abide it when the cement isn’t flush with the lead and smooth.

      Whiting: a little is useful for speeding up the drying time, we find. A little: I have painful memories of the cement-shop where I first worked: sometimes things went too far, and it got dusty like a bread-factory, and quite unpleasant.

  15. Please don’t leave it too long before you post Part 2 of “Cementing, Cleaning and Polishing a Stained-Glass Window”.

    I am on tenterhooks waiting to know whether to buy some off-the-shelf cement or get some more all-purpose putty and add my own white spirit, boiled linseed and acrylic black paint. There is not much left in the bottom of my small bucket and I’ve got six panels to finish.

    I am really eager to hear your expert advice.

  16. Geoffrey Wallace claims, and I agree, that the plaster (which is bathed in the boiled linseed and turp mixture) never matures, so the hydroscopic reaction never occurs. Boiled linseed oil dries not rock hard but like shoe leather, providing a very secure but still slightly “soft” hold for the glass within the came. Just feel the spill at the top of your used can. Of course I’ve only been at this for 40 yrs. – always learning. Last week after hundreds of old window treatments, I figured out a new fiddle with two awls for pulling the nails out of a frame without tearing the borders: the second awl, flat on the frame acts as a fulcrum, while the first awl digs head out of old cement, bends it away from border came – and up it pops, so easy. Duh, haha! Geoff

    • When the plaster/putty in new there is no hydroscopic action. But all the oils in time will dry out. This is when the plaster becomes hydroscopic. This is Geoffry Wallace’s premise that allows him to do in situ reputting. My problem is if this reputting does not take place the plaster will absorb moisture. Part of this condition will show itself in what is referred to as “plaster bloom”. This is a leaching of plaster on the surface of the glass near but not under the came. This bloom will hold moisture and other stuff that can attack the glass.
      ” Of course I’ve only been at this for 40 yrs. – always learning.”, same for me

  17. Hi Guys,
    Many thanks for the various narrative relating to the cementing process. I use “Off-the-shelf” cement that is made by a local manufacturer of regular glazing putty. It works well, but recently have found that when I get to the polishing stage I find the glass is left with an iridescent sheen – almost like the glass has been silvered. This effect is very annoying and extremely tedious to remove. I usually have to go over the area with a small rag wrapped around a bamboo stick after soaking it in mineral turpentine. Any ideas for preventing this outcome would be greatly appreciated. (I don’t use whiting or talc in my final clean up. Would it help to do so?)

    • It’d be a quick experiment to see whether whiting helped. So, given that what’s happening right now is a nuisance, this test is certainly worth your time.

      Not too much whiting, though: you sprinkle it on, then use a cloth or a brush (like the ones which come with a dustpan) to push the dust around. A little goes a long, long way (and a lot will make your studio dusty).

    • It depends on the climate and also on the ingredients: both these factors determine how long it takes for the cement to set well.

      Here in England, and with the cement which we make ourselves, we leave ours for several weeks at least.

      But we ourselves must be safe rather than sorry: we absolutely can’t risk installing windows in a client’s home only for them to start oozing.

      Best,
      Stephen