Turns out WD40 is an effective solvent for the glue - both dried-out and still-sticky - on an unidentified flavour of double-sided foamy tape.
How did I discover this, I hear you ask? Well... the place we're coming up to 5 years in has some built-in wardrobes, with mirrored doors (smoked, unfortunately, which reduces their utility). I guess they were put in maybe 10 years ago - they postdate the house itself (20odd yrs). Each mirrored door is 50cm wide and floor-to-ceiling high; the mirrors are stuck to the chip doors with 7? strips of double-sided foamy tape. Those held long enough to avoid the installers being called back by whichever previous owner had the work done; but as of today, all three of the doors on the side which gets more sun, and two of the four on the other side, have slipped down and needed regluing with Something Better. Only two left to replace - and they're showing the first signs of slipping down; fortunately, they don't detach suddenly, spectacularly, and mirror-smashingly, but rather droop slowly off the doors.
So, there's an all-too-well-established ritual here - complete the mirror detachment which time&gravity have set in place, take the door off its piano hinges (thank the Pope for the light electric screwdriver whose praises I sung here a few days back - there's forty-odd of the little bleeders ;-), scrape off the remains of the dbl-sided tape. For the door - Contiboard or similar - mere mechanical scraping is pretty much all that's needed, as one can give it the requisite welly on a surface which'll be hidden (and the odd scratch on will just improve the keying of the replacement glue). The mirrors, though, have silvering you really don't want to scratch off! So, I've tried a variety of solvents on previous occaisions. The most effective has been a label-remover from ?Canford Audio? called At-Tack, but there's not much of that left in the bottle... So, I got all systematic, trying - meths - the old grotty Dutch gin I'd already use on the doors - WD40 - and the At-Tack on the first 4 strips, leaving it to soak for a few minutes. Surprisingly, the WD40 was the most effective, closely followed by the precious At-Tack, while the two alcohols didn't soften and release the adhesive much at all. The remaining 3 strips and the ones less well removed by the alcohols came off well with the WD40; a final coating of isopropyl alcohol and wiping up quickly with kitchen roll removed the residue of WD40 well enough.
The adhesive I've used - today and on each of the four previous mirrors
- is 'Timebond', a thixotropic contact adhesive, which gives a tiny bit of repositioning capability; 'tiny' because the combination of weight and considerable surface area - a tad over 1sqm - means the mirror doesn't exactly 'slide' over the door once it's lying on it, but a couple millimeters of straightening up is possible.
And yes, I've had the windows wide open on both sides of the bedroom, to let the glorious mix of: WD40, ethanol, methanol, At-Tack, isopropanol, and toluene (the Timebond solvent) at least mostly disappear before bedtime! Ahh, organic solvents [cue Homer Simpson noise... ;-]
Stefek