Replacing old putty in Sash windows

DamoKen

Hi, I'm doing some repair work on old sash windows. First step before stripping the paint is to repair/replace the old putty which is either cracked/crumbling or just missing in a lot of places.

Never did it before so spent a fair bit of time researching and started on the first over the weekend. Using a heat gun (very very carefully!) I managed to remove the majority of the putty and sanded afterwards. Glazing points were in reasonable condition so I left them in place.

Now next step is where there seems to be differing information. Lot of blogs/threads just go right to kneading the linseed putty into the right consistency and applying neatly. This is what I did.

However read a few more sites since then and see that a lot consider a primer before the putty to be essential, otherwise it will crack and fail within weeks of application. Reasoning behind it seems sound, i.e. linseed will be absorbed into the wood drying out the putty plus the putty will not adhere well to the wood without a key.

Is this accurate? If so what would be a good primer? Most are very vague, just say primer but one restoration site recommends a coat of shellac instead.

Would this be as effective? I've loads of shellac in the work shop and kind of like the idea of between it and the linseed putty going with a traditional approach to restoring the 180 year old sashes.

Cheers

swailer

I've never seen a heat gun being used, a glazier will use a hacking knife and a hammer to remove the old putty, which does take some skill to master without hacking the frame to bits! Then simply apply the putty straight on the wood without a primer.

bonzodog2

I'd strip the paint first, then redo the putty, the re-paint. Maybe easier if you can remove the sashes; good time to change the sash cords too.

DamoKen

swailer wrote: »

I've never seen a heat gun being used, a glazier will use a hacking knife and a hammer to remove the old putty, which does take some skill to master without hacking the frame to bits! Then simply apply the putty straight on the wood without a primer.

Hi Swailer, so you reckon a primer between the putty and the frame isn't necessary?

Re the heat gun, most of the forum threads & youtube vids I looked at either mentioned a hair dryer or heat gun if you had one to soften the putty.

As I already have a heat gun gave it a go. Need to shield the window to prevent it cracking but seems to work. Quite slow but think that was more paranoia on my part that I would crack the pane if I left it on too long. I may do a test on a pane in the workshop which already has a few cracked panes that need replacing to get a feel for it.

Hacking knife looks like a decent alternative though so might see if I can source one at a reasonable price and compare. Thanks for that!

DamoKen

bonzodog2 wrote: »

I'd strip the paint first, then redo the putty, the re-paint. Maybe easier if you can remove the sashes; good time to change the sash cords too.

Cheers bonzo, I did consider doing that, glazing would definitely be easier but reckon it might be a bit late in the year to start. Got a load of other essential jobs to get done before Winter and a pregnant wife who may not appreciate her bedroom windows going missing in action

At the moment I'm just looking to protect the exterior over the winter. Come Spring I hope to have the time to do a proper repair on each sash, and yeah replace sash cords etc where required.

Thanks

swailer

Can't say you don't need a primer but in 33yrs I've never seen it used.

DamoKen

swailer wrote: »

Can't say you don't need a primer but in 33yrs I've never seen it used.

Grand, I'll leave the one I've done as it is so. Might put a bit of shellac on the next, loads already mixed so five minute job. Be interesting to see if there's any difference over the next couple of years.

Cheers