Don't know about silk, but silkspan is made from plant-based (vegetable) fiber and it will rot over time, especially if it is left out in the open air. Light will also affect it to some degree. If you have any "old" silkspan and it appears to be yellowish or brownish, don't use it! Lou Wolgast used some aged and discolored silkspan on one of his planes and then put a contest finish on the ship. When he started flying the plane (a JD Falcon) the silkspan tore diagonally between the rib bays. Lou had to completely refinish it.
If the silkspan still appears to be white, it should be fine. Of course we are talking about the old silkspan. The new stuff is just horrible. The story I heard is that silkspan was primarily used in making tea bags (although it reportedly was also used as dress lining material), and it was found to have a carcinogen that was a byproduct of the way it was manufactured. As the story goes, when they removed the carcinogen from the process, they also removed the qualities that made it desirable for our use, and the result was the dismal stuff that is in kits these days.
When Lou refinished the Falcon he used Polyspan. Interestingly that material is also used as dress lining!
I still have a bunch of the old silkspan, and it is still pretty white. I keep it in a plastic sleeve and in a box away from light. My old - and now sadly departed - buddy, Phil Granderson sent me a bunch of the "good stuff" a couple of years before he passed.
Perhaps someone else can enlighten us about the shelf life of silk...
Later - Bob Hunt
PS: Found this on the internet:
Plastic-free tea bags usually use a bioplastic that is created from maize or corn starch. These plant-based materials function the same way as polypropylene does. Bioplastic can also come from genetically modified (GMO) maize although they are not allowed in organic teabags.
Topic: Old Silkspan & Silk (Read 550 times)
