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.
The great benefit of bought cement is:
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 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.
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.
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.