Done I bit of testing/experimenting over the Christmas holidays with kite recoating.
firstly I worked out what solvent dissolves silicon the best/fastest/easiest. I tried acetone, turps, mentholated spirits and shellite.
i worked out that shellite was the best option. Dissolves the silicon easily and evaporated quickly.
the way I made up the mixture to coated the test pieces was to mix about 1 part silicon to 10 parts shellite in an ice cream container. I just mixed it for a couple of minutes then poured the liquid into a pump up garden sprayer. Make sure not to pour any remaining bits of solid silicon into the sprayer and only do it when you are ready to coat the kite. Have everything ready and work quickly.
i made up a porosity tester a while ago, so dragged it out. The tester is calibrated and doesn’t give results that can be checked against a database. But it does give a guide and can be used to compare old kites to new.
The cloth is sandwiched between the 2 seals, held together with magnets. It creates a vac by lifting a water column inside the bottle and you can simply time how long it takes to drop between marks on the bottle.
I used an old flogged out peter lynn s-arc for the test and a bit of brand new chickara from a cut up f-arc.
i first tested them uncoated to get a starting point.
i then put some pin holes in the fabric and retested.
next came the recoating. I lay the kite on the grass and sprayed the test area. making sure the cloth was well wet.
Do NOT spray on cement, timber decking, etc. any silicon overspray will creat a VERY slippery surface.
I let dry for 24 hrs and retested the porosity. I was amazed. The difference was HUGE!
the fabric isn’t now crunchy, but feels soft and slippery. And is extremely hydrophobic.
I don’t think that it will improve the strength of old fabric or how long it will last. But it will definitely improved the ability of the kite to hold air. The next step I guess is to coat an entire kite....
test area 1 uncoated - 2:17 (average over 3)
test area 2 uncoated - 1:58 (average over 3)
control area 2 - 15:00 (calculated as it took 5 minutes to drop 1/3)
test area 2 with 3 pin holes - 1:35
test area 1 coated - 15:00 (calculated)
test area 2 (with 3 pin holes) coated - 18:00 (calculated)
so it has not only improved the porosity, but actually increased it to a level greater then the new fabric.