Seldom do I find an occasion to take exception with any advice
offered by my good friend, Bob Taylor, however I would like to make an
observation about his comments in MMD 150328 regarding windway sealing.
While "shellac" has been the historic "go to" material for sealing
pores and small cracks in wooden windways, this is one application
where a modern material might be a better choice.

Shellac has several drawbacks.  If you buy it commercially, it has a
shelf life which can vary.  Storage conditions (mainly temperature) on
their shelves and yours can also affect it.  You can mix it yourself
with alcohol and shellac crystals, but you need to get the proportions
right.  A frequent failure is that you have a solution that will remain
gummy and never dry completely.

My choice for a pourable sealer is a product made by Parks called Pro
Sanding Sealer.  See

http://www.rustoleum.com/product-catalog/consumer-brands/pro-finisher/waterborne-sanding-sealer 

It is a water based, clear liquid with little odor, that is easily
poured or brushed to form a durable air-tight film on wooden surfaces.
It seems to work equally well for vacuum or pressure applications.  Most
importantly, it is slightly elastic, so that dimensional chances in the
treated surface due to swings in temperature or humidity will not cause
it to crack as can happen with shellac, which (typically) dries to a
rigid film.  I get mine at Home Depot where it is priced at $30 a
gallon.  Certainly not cheap, but less expensive than other sealers with
similar properties I have tried, such as thinned Elmer's Glue-All or
PVC-E plastic glue.

As always, your mileage may vary.

John Grant