Opinion on shellac and glaze rabbetts?

[GibsonGM]

I know that some folks prefer to apply a shellac to their glazing rabbets rather than BLO or bloop...any opinions on this?

I can see an advantage: shellac dries very quickly, so you could prime and be glazing a couple of hours later.

Drawback: does not penetrate to act as a preservative....no clue how it would behave with any existing 'lumps' of dried glazing that got left behind when stripping...

Thoughts?

[phil]

I think you should use an oil, danish oil tung oil , blopentine. don't put shellac where the glazing putty goes. It seals the pores and so doesn't allow good putty adhesion also shellac has a very low melting temperature so if the window gets hot that might cause it to let go. shellac can not take a hot environment. I saw it fail where I put stuff in the attic, it all bubbled up.. also I used it as a sealer on my countertops and where the front edge is near the stove , same thing it bubbled up. It' cant' take heat.. do windows get hot? probably not, but might depend where they are? You can probably use it on the inner facing parts of the window if you just like the look of it. and that might be original. I'd oil the whole window frame , then later if you wan tot put some shellac on the inside that would be ok overtop.

[Willa]

Shellac's drying time is definitely a consideration.

I have used an oil primer on the rabbets on some windows and shellac on others. I did find that the shellacked surfaces were tougher to get the putty to stick to. I used both a linseed oil putty (Allback) and that terrible DAP33 on different windows. However - this lack of adhesion was slight. In windows that had tough lumps of old putty my main consideration was to use a similar putty to make a chemical bond with the old putty, which I avoided priming or shellacking.

If you are trying to beat the weather and even 24 hours can make a difference then go with the shellac ?

[GibsonGM]

Yes, really thinking that you could possibly get more done if you shellacked them...heating my shop with wood stove for this project and running out 6x in the night to feed it might be challenging, ha ha.

BUT - yes, I'd had concerns about shellac affecting the bond...not letting your putty really bond to the wood rabbett. So I'll do the usual, bloop, wait, putty. I"ll let the bloop dry in the shop, then glaze and bring the sashes indoors to store in the cellar where it's 40F minimum all the time...they don't go back til spring. Unfortunately, we're having a cold snap in Maine... -15 next week, so you can see temp is a concern, LOL! Arrrgh.

[phil]

I use dainish oil rather than blopentine, but I mix it about 50/50 with turpentine so it's quite thin. I find it dries faster. the first coat usually wicks in anyway but once you get some penetration those coats dry faster. youll see it in different colors ut I only use the clear, they call it "natural"

[Willa]

BUT - yes, I'd had concerns about shellac affecting the bond...not letting your putty really bond to the wood rabbett.

I don't think the shellac has a negative effect on the putty, or won't bond to the putty as it dries. I think it is more that it is a slick surface that the wet putty is slightly resistant to. None of the windows I shellacked have loose or failing putty so far ?

[GibsonGM]

Cool, Willa...I note that some of the windows I strip DO have shellac....you can tell once there is no putty left. Shiny surface and clean as a whistle.

Not all the windows I glaze have this, some were done 'dry', some with oil prime or linseed oil, some with paint (!), as homeowners over the years really beat on them quite a bit! There's a lot of variety out there

[Mick_VT]

Shellac is what I was taught by my uncle many many years ago and was the norm in the uk for those in the glazing business for generations. It's simply there to seal the wood, which shellac is great for. It stops the wood wicking the oil from the putty. BLO would have the same effect by saturating the wood and may provide other benefits, but I just do what my uncle taught me - not had any issues so far with either Sarco or DAP going this route. I love the speed of it I must say

[heartwood]

I use blopentine on the entire sash because the wood is dry (and the turps tend to dissuade mold and bugs)...I then prime with oil primer (not the rabbets though just because it's not necessary)...the blop is a good substrate for the putty and for subsequent coats of primer and paint whether oil or water based...it's not just a consideration for the putty adhering...because I am a professional, I have the luxury of time...we overlap projects so there's no down time...

because top coat products change constantly, it's difficult to study products over a period of time with any consistency...

that being said, I shall forthwith remove myself from applying any type of blop, putty or paint for at least 3 days!

.....jade

[GibsonGM]

Oh, DOWN TIME?? Enjoy it, Jade

I'm the 'painter first who also restores sash', always looking for new tips and tricks. Just wondering if shellac could cut my production time, but I doubt it. Why mess with a system that works? I have tried many ways, and find what you suggest to everyone, Jade, to be the most reliable, consistent and so far, long lasting process...

Unfortunately, my sashes come in "lots" of like 20 to 40, once or twice a year. So once I start heating the shop, it has to stay warm til the project is complete (or hits a stage where cold is ok til next step, of course). I get that screwy feeling when I start to mess with what works, on a paying job, where you think maybe saving some time and firewood may cost down the road, ha ha....so no alterations! Having to keep it above freezing for 36 hrs. isn't so bad...

Can't bring sashes with bloop inside the house or my wife will kill me Smell...