Two and a half days of scraping later....
More aggressive methods have given way to heating and scraping: it turns out that takes less leverage and when work switched to a ladder -- you get the picture.
Given the darkness of the old wood (which may be hard pine; hard enough to last nearly 90 years, at least), the first coat will be White Primer Of Overwhelming Force (plus I misplaced my sample chips; we're at that awkward stage, a Valspar color matched in Behr paint*). My painter's got a vacation next week, so the deal is, "Leave no bare wood."
This should establish a nice blank canvas to try out the fancy housepaint in an inconspicuous spot, plus do some prep and small work like screen frames -- I've got at least one screen (wooden frame) that wants redone anyway.
The Indy Hamfest is this Saturday! So that's a day to let the paint dry before I go tryin' anything.
* Which means that no matter how good modern paint-tinting has become, I'll be wanting to get a big order done up in one go, and will be picking up one or two five-gallon mixing cans; you pour all the one-gallon cans together and then even if the Big Magical Machine had a valve stutter or whatever, the color will be consistent).
2 months ago