Chris, I am really enjoying watching your truly inspiring progress on this thread.
I am rather sorry I missed your proposal for using masking tape to represent tarred felt - especially as you have now gone on and made such a superbly crafted job of it!
I would have shouted sooner if I had spotted it!
Masking tape might appear to be quite benign stuff, easy to use, convenient, and indeed useful to the point of being essential - yet it has a very nasty habit:
The adhesive commonly used is notably unstable. After a while, sometimes quite rapidly, it breaks down into a slime before drying out to a powder! During the first stage the tape will come unstuck and can curl up, releasing some of the goo, which can spread out. Finally, when it dries, the paper tape shrivels as well!
Incidentally, "Double sided" plastic tape or sheet can, and does behave very similarly!
I speak from bitter experience, and over the years have had some very precious and irreplaceable artwork utterly ruined by the use of both these materials.
Anyone tempted to use either really should be made aware of this.
To all readers I would say:
Only use masking tape for temporary tacking and, or, for the job it was actually designed to perform...
...and please, please avoid double sided tape like the plague!
By the way, I have found that tissue, stuck down over a thick, wet layer of paint, and with a further thinned coat of paint added on top has proven to be the most effective, and durable, method of representing felt for roofing.
I have even used this method on garden railway rolling stock that has not only been subject to extreme weather conditions, but significant oil contamination from live steam engines as well - and all with no detrimental effect whatsoever!
Pete.