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After about 80 hours the surface still felt a bit sticky (no further improvement during the last hours). Therefore I hang it outside. I think there it must completely dry within a few hours even in the shadow. I made already a water test. As far as I can see it is 100% waterproof. No need to repeat the treatment. The character of the fabric changed completely. The fabric is evenly much darker (a nice brown-olive) and water drips off fast. Before the treatment the ripstop nylon soak up any wetness and got promptly spotty (This was the reason why I did not want to use this fabric for my hammock project). Tomorrow I will put it on the scale. Before the treatment the 12' hex tarp was 10.4 oz.
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The silicon sauce I used was 42.6 oz (1208 grams) heavy. I used this material completely for a 12' hex tarp + Grizz beaks. After the treatment I noted the following weights and alterations:
Code:
before after
treatment treatment change
oz oz oz %
12' hex tarp 10.4 16.2 5.8 55.7
Grizz beaks 7.5 8.7 1.2 16.0
total 17.9 24.9 7.0 39.1
This looks a bit strange. But the explanation for this is that the material was already a bit short for the Grizz beaks. 7/42.6 ~= 16.5% means that the sauce volatilized by ~83.5% during the drying process.
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I have shown the finished tarp after silnylon treatment here.
The tarp is 100% waterproof and I can use it. But I consider this experiment as no success. The silicon coating is imo too soft and very sensitive. And I still have the impression that the tarp is not really dry and the surface feels a bit sticky.
I would in no case repeat this experiment. I would prefer Silpoly PU4000 2nd Gen. In a similar situation than I was (I had the ripstop nylon fabric left over and didn't want to use it for another purpose) I would try it with some water resoluble acrylic mediums which artist use. There are some acrylic binder on the market which are highly elastic and very durable.
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Just finished my first DIY tarp and wanted to share some of my successes, failures and thoughts on DIY Sil.
My son needed a tarp for his hammock when he heads off on his Boy Scout high adventure trip in a few weeks, and found some polyester fabric in a camo print he liked so we bought 7 yards and proceeded to sew up a simple rectangular tarp (123"RL x 116"W). Following the recommendations in this thread (I read all 513 posts!), I bought a couple of 3 oz. tubes of silicone and some odorless mineral spirits from StuffMart with the intention of using one tube per half of the tarp.
We pitched the tarp in the backyard and I mixed up the sil in an old pickle jar using my drill with a length of wire coat hanger bent into a crude mixing paddle.
Lesson #1: A length of coat hanger will not stay centered with the rotational axis of the drill but will flail wildly about once it gets up to speed. :scared:
I now have a waterproof pair of shoes and socks (and legs and 4' dia. patch of patio).
Solution: Drill a hole in the pickle jar cap to pass the coat hanger through, and have someone hold the jar while you mix.
My second batch of sil was ready to go after about 3 minutes of mixing and my son and I started painting it on the tarp with 2" foam brushes.
Lesson #2: This is a terribly slow and tedious method for applying sil. We were doing this outside on a cloudy Saturday morning and I found it nearly impossible to see where I had applied the sil. This was (I think) partly due to the lighting conditions we were dealing with and partly due to the fact that the fabric gave no visual indications that the sil had been applied here or there.
Solution: Not sure. After a few minutes of this, what I *wanted* to do was lay the tarp out on a table and pour on the sil and spread with a sponge (like you would do when applying wallpaper paste to wallpaper).
My son and I painted for about 15-20 minutes before we felt we had covered the first half of the tarp. We used all the sil I had mixed up and both of us were pretty sure coverage was questionable at best. By the time I was able to run back to the store to pick up another tube of silicone, it was late afternoon and about 10° warmer in full sunshine. I mixed up a third batch of sil and applied it myself to the other half of the tarp. I had better lighting now but still had trouble seeing where I had applied it. And I was wearing latex gloves.
Lesson #3: In the morning my son and I wore nitrile gloves. In the afternoon I grabbed a pair of latex gloves by mistake. Latex falls apart in mineral spirits and silicone and I had to stop and pick pieces of latex glove off the tarp as I was brushing on the sil.
Solution: Stick with nitrile gloves.
We gave the tarp 48 hours to cure. I was surprised by how thin the coating felt on the fabric, I expected it to be heavier. I could also feel that the coating was uneven. We blasted it with the garden hose to see how waterproof it was. As expected, not so much. The tarp half my son and I did together appeared to be about 85-90% waterproof with water misting through in only a few random spots. The half of the tarp I coated myself in the afternoon was a disaster! It had maybe 50% coverage with water misting through everywhere.
I didn't want to give up on this tarp (especially after all the work that had gone into it), so I bought more silicone and mineral spirits, more nitrile gloves and a large sponge (StuffMart was out of wallpaper sponges that day, so I picked up the largest Ocelo kitchen sponge I could find).
We pitched the tarp inside out (to coat the inside surface this time), mixed up a double batch of sil and got to work. My son held the fabric taut so that I could pour on the sil and spread it around with the sponge. We sponged the entire tarp in about the same time we spent brushing just half the tarp the week before.
Lesson #4: Skip the brush and use a sponge. If you can do this on a large table or clean floor, even better! Also, the kitchen sponge worked great, although a larger size would have been nice (mine was about 4"x6").
We still had a difficult time seeing the line between sil/no sil. My son acted as my spotter while he held the tarp and we both paid closer attention to make sure we didn't leave any areas uncoated.
After another 48 hours to cure we blasted it with the hose again. This time: Success! We could detect no misting or leakage with a heavy spray from about 3 feet away. The coating is thicker now, obviously, but still thinner than I ever expected. It doesn't have a tacky/sticky feel like others have experienced but it IS very grippy. I could use a scrap in the kitchen to get those stubborn jar lids off. :lol:
This method of tarp making isn't for everyone. You need to plan ahead, be patient, have a good area to work in (outdoors is doable, but indoors on a table would be ideal) and think it through before you do dumb things (see lessons 1 & 3).
Cost wise, I spent about what I'd spend on a RBTR tarp kit. But only because I used so much more sil than I planned. The fabric, thread and grosgrain were about $20. Silicone, mineral spirits, brushes, gloves and a sponge came to about $36 (including the waste). So $56 for the whole project. The project should have cost only about $40.
Would I do it again? Yep! (started sewing one for myself last night) Because I like to make stuff. I like the satisfaction that comes from creating a piece of gear that you can't get by buying it. Mistakes and failures are part of the learning process so no effort is wasted. I learned this years ago building my own ham radio gear.
Anyway, I hope this helps someone make a better informed decision about their own DIY Sil project. Cheers! :shades:
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For anyone still looking for a more thorough tutorial, this guy's video is really great:
https://www.youtube.com/watch?v=z_R0gEDZhAI
