During my last tarping trip through Sarek last September I’ve become pretty wet two times under the tarp whenever it kept raining over a prolonged period of time. The silicone coating had almost completely disappeared from the tarp (actually you can say that it was completely gone). With spring and new plans coming up, it’s time for a new coating.
Just before the start of my trek through Jotunheimen in July 2007, the first time that I used my MLD Grace Solo Spinntex .97 tarp, she weighed 196g on the scales. 186g is wat is left today when I returned from Sarek. So there must have been 10g of coating lost over 4 years. That might not seem that much but the spinntex Mountain Laurel Designs used at that time had actually a very thin coating. Today, Ron Bell uses a silicon impregnation about twice as thick on its spinntex (called Spinntex EXP).
So I pitched the tarp in the garden and prepared a mixture of white spirit and 20g silicone with a 15:1 ratio poured into a cup. This is a very thin mixture (normally a ratio of 10:1 is recommended), but this has the advantage that you have more control over the thickness of the fresh coating. So I’ve applied one layer on the inside and two layers on the outside of the tarp. The tarp weighs now 201g. That is a total of 15g silicone applied to the spinntex, or a coating of 2g/m² on the outside (the other 5g silicone is left on the wall of the cup).
Afterwards I tested the water resistance by pouring water sprays on the tarp for some minutes. The bottom stayed now bone dry as it should. The spinntex feels less rough in the hands now. You can feel a clear coating on the material again. So I’m again ready to go out tarping in the wilds!