You already know how necessary your cement is – it gives your window strength and seals it against the wind and rain.
So let’s now consider that important question: ready-made cement vs. when to make your own.
Bought cement
The great benefit of bought cement is:
- Convenience.
How amazing is it that I can just unseal a lid and start cementing? It’s wonderful, and I’m so grateful for the edge this often gives me.
Now as I see it the main disadvantages of bought cement are:
- You can’t be sure it’s in prime condition. Certainly you can check the “Best Before” date. But the point about cement is, it sets. So, if it’s in the store a while and no one’s turned it, it’ll start to harden. And there’s nothing you can do about that except try to take the tub back.
- You can’t be sure the ingredients are the very best. The manufacturer can replace one kind of oil with another on grounds of cost, and, 15 years down the line, we find out the consequences. We find them out the hard way. But actually it’s far worse than that: our client finds them out. (See this comment here from Gerry Eversole about the what’s wrong with soya bean oil, for instance.)
There are also smaller disadvantages:
- You will probably need to fine-tune your bought cement to your own tastes for the particular project you have in hand. It’s easy enough to do with boiled linseed oil. But it takes time and makes this off-the-shelf cement a little less convenient.
- You’ll end up with left-overs. (You can of course transfer them to a smaller tub, pour in some boiled linseed oil, seal well, and then – most important – turn fortnightly, but this is something I always forget to do.)
Our approach
Our approach is: we never try to save money by buying our cement from a local builders’ merchant, for instance.
Rather, we pay a substantially more expensive price for a reliable brand, recommended to us by someone we trust who himself uses this particular cement several times a month (whereas we use cement only twice or three times a year, as each big project nears completion).
Ourselves, we tend to use bought cement for large projects.
And so we make our own for those occasions when we have a single window or we’re restoring a single broken panel from a church for instance.
Make-your-own
Many thanks to Geoffrey Caldwell, Mary Ann Celinder, Barbara Bennett and to Vic Rothman for sharing their recipes.
We ourselves use:
- Whiting and plaster of Paris, combined in proportion 75:25 (see here for a timely warning from Vic Rothman concerning the water-absorbent property of plaster);
- Cement black;
- Boiled linseed oil and turpentine, combined 50:50.
Yes, it takes a few minutes to make your own. (But sometimes this is quicker than ordering in, or driving to the shops to buy some.)
On the upside, you get good at judging how much to make. And you can also make it just the way you like it.
A compromise
Now, as Catherine M. and Ali Bishop both point out: you can also buy small (or large) tubs of glaziers putty (made from linseed oil), darken it with cement black, and thin it with further linseed oil to whatever consistency you need.
Different projects, different climates …
All we can do is say, “Here’s what we do, and here are our reasons …”
Everyone must be guided by their own experience:
- What to do with thin leads, what to do with thick leads;
- What to do with thin glass, what to do with thick or plated glass;
- What to do when it’s particularly hot or cold.
And so forth.
As Matt Kolenda observes, it all depends.
Which means it’s wrong to codify or seek to legislate.
After all, we’re all striving to do the right thing, and the most important achievement for all of us is to learn what other people do and why.
Huge thanks from us
Huge thanks from Stephen and me to everyone who joined in the discussion and shared their knowledge.
Further recipes and contributions are always welcome: so please use the comments box below.
I bought a pre-mixed gallon can at my wholesale glass warehouse. It was completely separated upon opening – float of liquid over an almost rock hard gunk. They wouldn’t take it back and it hadn’t been cheap. Called the maker (inland): they said I’d just need to stir it. Baloney. I spent easily 2 hours using a power mixer to finally get it useable! Soooo much easier to make myself. I will take the whiting tip to heart and change my mix. Thanks again for posting this discussion.
Helpful story about the pot of hard cement: thanks for sharing.
I’d love to know how much make-your-own cement you find it practical to make up at one time. Here at W&B, we’ve tended to make-our-own just in small quantities, and use off-the-shelf those two or three times in the year when we settle in for a week of cementing: and so I’m really interested to know more about your approach.
About plaster vs. whiting, Geoffrey Caldwell shared a further observation here.
I used Inland cement for years before discovering that it leaks, which also leaves unsightly marks on the glass which are very difficult to remove. Tested it by dribbling a hose down one side of a mature display window (well sealed) for a couple of hours – and, sure enough, it was seeping through and running down the inside.
It also hardens like rock making repairs much more difficult.
Much happier making my own.
Which oil do you use when matting
Can you help me here: how do you intend this question to relate to cementing and polishing?
David, Is there any way you could film the demo again with small circles traced with small squares in the center like a sunflower/honeycomb?
That isn’t possible because it would take time we must give to other work.
I have always made my own too. Generally, I use ordinary Portland cement from your local builders merchants. Powdered cement dye (black) also from builders merchants & boiled linseed oil.
I first add the oil into a suitable container, then add the black cement dye, so that there is a runny black liquid. To this, I will on occasions add a few drops or Terebene dryers, to aid drying in cold conditions. Then I add the powdered cement slowly to the liquid, until I reach the consistency required.
Once applied, with a stiff brush, I then sprinkle the panel with whiting to absorb the oil, before buffing excess cement off with a stiff brush.
It has to be said, this is the most loathsome part of making a leaded panel!
A TRIO OF STAINED GLASS CEMENTING COMMENTS:
Intro:
Having had the pleasure of learning cementing of many a stained glass panel during training, a couple of important point have been learned that seem appropriate to share with the readers of the blog. My training took place in Detroit, Michigan, USA starting in the summer of 1964. Cementing and lead stretching were the two main chores of the job. Other responsibilities were to get the morning coffee for the other employees, drive the broom whenever necessary and keep the bathroom clean.
ONE:
The cementing portion of this job was the main time consumer and it helped to develop blisters and eventually calluses on the ends of most of the fingers on both hands. We used the thumb technique exclusively. This help to develop ambidextrous skills in case I decided to become a professional guitar player. Other parts of this main job were to prepare the cement which was adding additional ingredients to the commercially available gray steel sash putty which was supplied in 3 gal. buckets. This included “lamp black” which darkened the gray color. It’s really amazing how little of this black powder is needed. The second addition was to add “red lead” to the estimated size blob of putty. Red lead is really red and the reason reason given for adding this powder was to help mixture harden. If you do restoration or repair work you may have run across some old cementing that appears to have some red coloring. Please be aware that this is now considered extremely dangerous to your health. We are much more conscious of these types of dangers today. There were no warnings or percussion at that time. Beware!
TWO:
The second concern with any discussion on cementing is the idea which some individuals invented during the early 1970’s. This concept is adding Portland cement to a “from scratch formula” to give it strength. If you do repair or restoration work you may have run into this disastrous concoction. The concept must have come from the reasoning, “Who needs to know specifications for size and the need for support bars if you use Portland cement?” “Besides the bars only distract from and interfere with the design”. If you detect some anger and frustration, yes it’s here. Some over the counter cementing products have offered this disastrous mixture to the unsuspecting students. This creates an amazing amount of complexity to any repair or restoration project which translate to additional time and money.
Here are some additional comment on the thumb cement technique. Although it difficult on the thumbs until you get use to it, you may find it easier to clean up afterward. And if you decide to take up the guitar, you’re going to get calluses on your fingers anyway.
THREE:
One last thought, it seems that the scrub brushes that are made of natures fibers work best. They’re the ones that the brick/mosaic masons use for the acid clean up. If used with powdered whiting and a little powdered lamp black mixed in, you can get a very nice rich and subtle sheen on your lead.
Remember: “If you cement the panel, you’re the first person to lay eyes on a great finished piece of art.”
Regards,
Tom Newton