Monday, 26 August 2013

How to putty a window

Free time.  But is time really free?  Actually, yes it is, but it's also the precious item of all.  And this summer my free time, which is but isn't, has been spent doing some renovation work on an in-laws house.  Running and fanning has to play second fiddle for a while.  I still get most of my runs in but no time for any other casual activities.

But back to this reno thing.  Part of this is prepping the front of the propery for 'curb appeal'.  This is where people will look at it from the curb and get that good first impression.  It's important in this particular case and having a very windowy but aging front porch makes either a lot of work or a lot of expense.  Work, in this being time, is cheap, because it's free!  New windows aren't so cheap.  So my precious but free time this weekend was to tackle the task of tidying up these windows for curb appeal.  Well, not quite all of my free cheap time, but most of it.

This almost 80-year-old structure has original wooden single-pane windows surrounding the enclosed porch and time hasn't been kind.  We had a laborer do the work of cleaning off the paint and was also to remove the old glazing putty.  Problem is that putty after that period of time is in nasty bad shape and also hard as rock.  We tried lots of ways of getting it off but couldn't do it without breaking the glass, and it was clear that it would take a tremendous amount of time to do it if attempting to preserve the glass.  So we picked plan B, smashing every window and pulling out the old putty.  This proved more effective as well as faster and the windows were cleared of all the old debris in a couple of days.  Too bad they were also now cleared of all the old glass as well, leaving a well ventilated front porch.

We were lucky that our window supplier offered to cut the glass panels, admittedly he wasn't expecting to cut 34 individual panels.  So it took a bit longer than expected and we reimbursed accordingly.  On Friday I was able to pick up my new panes of glass, carefully transport them in the back of the Mazda 3 with generous layers of paper towel keeping the panels stable and safely together.  I managed to get them to the site each in one piece and double checked the sizing of each.  The windows held either 3 or 4 panels each, with some windows differently sized.  The cut has to be no more no less than 1/8 smaller than the openings so size is crucial.  Fortunately, they were all bang on in sizing and worth every penny paid.

The window frames had spent 3 weeks covered in plastic to keep out the elements and keep the frames dry while awaiting my new glass.  With 34 panels to install, I bought all of the packs of pushpins my local Home Depot had in stock and still ran out.  Plus a pint of interior/exterior primer for the openings, 3 tubs of DAP 33 glazing compound and a new 2 1/2 inch flexible putty knife.

Saturday was clean the frames, prime, and carefully pin the panels in place.  And I had a couple of hours left to practice my glazing technique.  I had already checked out some info on-line, watched vids, an so on.  It's a given that it will be harder than it looks so practice was imporant before I get to the real thing.

Sunday was glazing day.

Now, the DAP 33 is thick and doughy.  The instructions say to mix thoroughly before using, easier said than done.  You have to disregard the 'avoid contact with skin' notice on the label, grab a handful and knead it up like a small ball of pizza dough.  After you play with it a bit, it softens up and is more workable and sticky.  Your hands and your knife handle will be covered in this stuff before you're done anyway.

At first, this seemed impossible as the putty just wouldn't apply properly, it would fall off, curl and tear, and so forth.  The couple of hours of practice were important, and trying different techniques, since I have a whole batch of these to do.

A few things become clear.  First, patience is critical.  Second, softening up the putty helps.  I rolled it in my hands like making snakes out of modelling clay and pushed it along the edges with my fingers a little at a time at roughly twice the volume I would need, doing the whole panel at once.  Third, clean the area below, it's not horribly expensive stuff but you don't want to waste it.  So get rid of all the dirt and debris below to reclaim what falls.  Fourth, putty knives are specially made for this.  They are thin, flexible, and have rounded dull edges,  Since you are gliding this thing right against the glass you don't want sharp corners scoring your panels, that's not good for appearance nor longevity.  Don't use anything else thinking it will work just as well, it won't so invest a few dollars in a proper knife, mine cost $7.

Now, when you pull the knife along the edge, this is where technique really comes into play and it takes practice to get it right.  These windows are old, they don't have perfectly straight square edges, there's little nicks and groves and dips in the wood.  The knife has to follow this edge so those grooves reflect back onto that nice flat straight bevel you are trying to make.  Here's where the flexibility of the knife comes in.  When you draw the knife, press into the middle of the blade to force the end flat along the bevel.  This does two important things.  Those nicks and cuts in the wood have less effect on the layer of putty because the flat blade glides over with less variance, which makes the putty nice and flat with just slight waving on the surface.  Also, if only the end of the blade is against the surface, the putty tends to curl and tear.  This is because it is under pressure at the end of the blade and releases once it's free, causing the above problem and leaving a messy line.  With more of the blade surface against the putty, it isn't under pressure when it finally gets to the end of the blade, and stays perfectly smooth and flat.

After a while it was easy to get a long clean bevel in one smooth draw.  You also have to learn to play with how the blade is oriented along its length.  Keeping it straight in line with the edge gets a good full volume of putty into the grooves but can tend to gather a lot of excess on longer lines.  Too much excess, the putty pulls away from the edge, while too little doesn't fill the edge properly. Slightly turning the handle away helped clear the excess when necessary.  You learn to play with the orientation a bit to get the best result depending on how long the edge is and how much excess putty is forming.

The corners provide their own challenges.  To start a corner, I set the end of the blade to form the exact angle and bevel I wanted, then turn the blade on it's corner point until it was straight along the edge, as I note above, and then start the draw.  When I reached the far corner I'd set that angle using the side of the knife instead of the leading edge, drawing the knife out and away from the window.  Then clear the knife of excess and repeat on the next edge.

Finally, when done you carefully remove the excess materal from the glass and the frame.  This takes a steady hand because it's a free handed action.  Move slowly placing the knife edge near the material and gathering it up...more patience.

The smaller panels were about 13 inches by 5 inches, and I had 25 of them.  I got to the point I could glaze and clean one in 5 minutes, down from 10-12 minutes when I started, and a lot neater by far.  The 9 bigger panels at 27 x 15 took about 30 minutes each when I started to about 15 minutes at the end.

You will end up with a lot of smeary putty medium on the glass, especially near the edges.  Leave it for a few days until the putty sets up,  The edges will still be soft even then so take care in cleaning the glass.  Painting it first might be best as the paint will offer some protection for the putty.

If you mess up, you can just start again.  I had plenty of mishaps and had to refill the edge with putty and try again.  As I went along it got progressively easier and better in the end result.  Just keep the key items in mind: soft warm hand-worked putty, press the knife down flat from the middle, and watch the excess material to clear it effectively.

And be patient, time is free, sort of.

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