I've made my own sealant in the past, but I took the more convenient option and bought a tube of sealant this time. Works very well and neat with the provided brush. Yesterday the weather was perfect for the silicone to dry; 20 degrees Celsius and a light breeze. It only took 2 hours for the silicone to dry sticky free.
I used the 1.1 oz Silpoly PU4000 to make a poncho with hood and sleeves modelled on a cheap but flimsy plastic one I bought in Vietnam.
The poncho seems to work OK but so far I have not needed to use it in torrential rain. (I use it over my normal wet weather gear and pack to keep most of the rain off. Like a tent fly, it doesn't need to be 100% waterproof to work.)
Some things to note about the 1.1 oz Silpoly PU4000:
1. The weight is a bit hopeful. I measured it at 1.8 oz (62 g/m²) not 1.1 Oz (37 g/m²). That is 66% more than advertised. Still, the poncho came out at 7.7 oz (220 g) about half a bought one but 4 times my flimsy Vietnamese one.
2. The website is a bit confusing about which side is which. The duller side should face the rain and the shinier side inwards.
3. It maybe "Ripstop by the Roll", but this fabric, despite having a ripstop pattern, rips easily, especially along the roll direction. Handy for cutting (!) but it meant I could not use snap fasteners which I had originally intended.
Used it today to seal my tarp. Seems to have great absorption qualities and cured nicely. Time will tell!
I used it to seal a tarp I made and it worked fine. The little brush that came with it is for single use. I tried it for another application and it was stiff.
i love this place!