Glazing putty is nothing more than clay mixed with linseed oil.
Mooshing (if that's a word) new glazing putty into the cracks would work, I suppose, if the new putty got deep enough into the crack. If not, I expect the "plug" would just fall out.
If it wuz me, I'd probably be inclined to mix a bit of putty with boiled linseed oil to thin it, and pack that in the crack. Or, maybe the boiled linseed oil might get sucked into the crack by capillary pressure, and you wouldn't even need any putty.
Also, the fact that the putty has cracks in it is most likely because the wood is swelling and shrinking with changes in it's moisture content, whereas the putty doesn't, and the result is cracks in the putty as it tries to stretch and shrink with the wood. The fact that it's still sticking well to the wood means that it's only the putty at the surface that's fully cured; the stuff under it isn't. That's the way putty works; the stuff on top reacts with the oxygen in the air, and that better and better prevents the air from getting at the un-fully cured putty under the surface. That un-fully cured putty will remain soft enough to allow for expansion and contraction of the wood without breaking loose from the wood.
Putty was used for decades before they came out with caulks. If you have lots of windows that are installed with glazing putty, and it's getting to be a chore always replacing the putty, I would probably think about using a caulk instead. After all, putty was used before they had caulks, why keep using putty now that we do have good caulks that will form a reliable seal between wood and glass? But, maybe use twice as many glazing points cuz caulk might not hold the window in as securely as putty.
If you're looking for a good caulk to use, look no further than Kop-R-Lastic, which is a synthetic rubber that has very good adhesive strength, but even better cohesive strength. That means that it sticks to itself even better than it sticks to the wood or the glass. The advantage to you is that when it comes time to recaulk, you simply have to get one end of the caulk loose, and then you can pull it off the window cleanly like a rubber rope. Since I started using Kop-R-Lastic, I won't use any other caulk.
http://www.usehickson.com/Koprlastic...ic_Guide.shtml
Kop-R-Lastic is made by the U.S.E. Hickson Company of Canada under licence from the Koppers Company of Australia, which is a subsidiary of Koppers Inc., whose head office is in the USA. My understanding is that U.S.E. Hickson has been purchased by the Henry Company Canada. I understand that the Henry Company is a popular brand in America, so I expect you guys should soon be seeing the equivalent of Kop-R-Lastic showing up as a Henry's product. Also, my understanding is that Kop-R-Lastic is not sold by the Koppers Company in the USA, and I have absolutely no clue why they'd don't market such a great product in their own country. I just don't make no sense no how to me.
http://www.usehickson.com/
But, if you have lots of old windows that keep you busy with replacing the glazing putty on them, I'd give some thought to replacing that glazing putty with a high quality caulk instead. Kop-R-Lastic won't work any better than any other high quality caulk, it'll just be much easier to remove the caulk when it comes time to recaulk.
Window Glazing - hairline cracks
Linear Mode
