Polycryo in consistently wet conditions

I use a sharpie and draw something on the “right” side. It may need a little refreshing after a 1000 miles but that’s ok.

I have used polycryo exclusively for a number of years now and have never had a problem distinguishing right and wrong sides. Whenever I fold up the sheet, I do it so that the bottom is folded onto itself first thing in half. I always simply unfold in the opposite manner. The last unfold tells me which side is top or bottom.

I don’t really care which side is which. Polycryo seems to dry out pretty easily even when folded up and shoved into your pack, and once it is dry you can just shake off the dirt that got folded up with it. If it doesn’t get all the way dry, the bad side is the dirty side. If things are super dripping wet, you’ll want to find a moment of sun during the day to try to dry things off anyway, or you’re just going to have to deal with whatever the weather throws at you and clean things off better when the trip is over. In the end, everything eventually gets dirty out on the dry and dusty. That’s the hiker’s life.

I write “TOP” with sharpie like Matt.  Anything that’s not the same in mirror image.

Like “ATOYOTA” wouldn’t be good : )

Matt, Eric and Jerry provided most of the input I was going to offer :)

One thing left to add, consider using the “double-thick” version sold as sliding glass patio door sealing kits. Duck brand at Wally World is one source. The slight increase in weight is very much worth the increased longevity and ease of handling.  I couldn’t deal with the “std thickness” polycryo sticking to itself when wet.  While not completely eliminated, the double-thick exhibits much less of this tendency. I also find that leaves, pine needles, duff, etc don’t stick as much.

Avoid the “X” or a smiley face :) because it will look the same from both sides…Just sayin’ (not that I know from experience or anything)

There are several considerations, generally.
There was thread, ummm….here: https://backpackinglight.com/forums/topic/dyneema-v-s-slanylon-tent-floors/#post-3585889

Anyway, Polycro is good, generally. Hard to beat considering all the actual requirements needed. In consistently wet conditions, a small mark as Matt suggests works well and lets you still maintain the many benefits.

Going with a membrane (nylon or poly) is a bit heavier. And stuff still sticks to them when wet. I do not think this can be eliminated from most of the UL fabrics. Water is actually a fairly viscous substance. It has a tenacity to other water (things that are wet.) It “sticks” to stuff. So, eliminating pine needles, dust, and other small things is nearly impossible. Dry it off, things can still stick, because water is a universal solvent, it will leatch out dyes, tars, etc making them remain stuck. Brushing it off after drying is usually required, for example. Switching from polycro to a nylon or poly membrane will not remove the sticking problem. Static can be a problem, but is usually gone by the time you have used it three or four times…I am discounting that.

Water vapour and liquid water are different. Vapour is a gas. It often penetrates right through silicone coatings. Fill a sil stuff sack with water, set it on a piece of paper overnight. Water vapour, will escape, and condense on the paper…maybe some actual water. A DWR will not work over wet ground. You will get wet, though not as wet as without it.

Membrane is not really for use as a floor. A DWR is not the same as as waterproof. For a floor, you need at least a 2500mm head. Otherwise the pressure (knees, hands, feet, etc) will actually drive water through it. I think it will likely require like a 3500mm head, but I usually err on the side of caution. One of the reasons I don’t care for silnylon stuff sacks and compression bags, they leak under pressure, as above. Membrane, as they are typically sold, will do the same when used as floors, as above. They need some sort of heavier treatment, usually PU, SilPU, or vinyl. For most of us here at BPL, we know this from R. Nisley’s great tests with various fabrics.

My home brew solution is to coat the floor material with a rather heavy coating of 100% silicone caulk and mineral spirits (not the “green” kind.) For example, a couple of my MYOG tents have a silnylon floor. These are coated to prevent leaks and seal seams. It works. But, even these will leak in heavy rainstorms for two or three days. A plastic coating works better, but the MYOG coating works well enough for BP’ing. I don’t stay put in one spot that long. What it does is to fill in the air spaces between the fibers and the fibers themselves with a thin sheet of silicone rubber making them waterproof as the mineral spirits evaporate. A 10:1 ratio, well brushed in on both sides, works well for floors. Eric B, uses a 5:1 ratio rolled on then wiped with paper towels. Whatever, it takes to press the silicone into the fabric with some pressure. At the factory, a couple knives press it onto the fabric to make silnylon or silpoly. It all works. Too thick and it can peel off. It adds weight. Thinned, it adds about .3-.5oz/yd to a floor.

The overall fabric with membrane can be a problem. Sharp objects, pressed on and around them, can cause punctures and/or stress tears…sort’a like pressing a pole against the floor. PU, vinyl exacerbate this by making the fabric less flexible. Silicone is very stretchy and does not. With the thin membranes, it is possible to tear them, often not exactly where the pressure is applied, but off to the side. This is worse than cuben, since it is generally larger. But, patches, are easily done with membrane/caulk. Patches with DCF/cuben are also easily done. But when the entire surface starts leaking, it is impossible to repair, only replace it. Membrane can be simply recoated. The overall thickness of the fabric is usually around 1 to 1.1oz/yd (using silnylon) to have a floor able to resist most punctures. For poly it would be closer to 1.4-1.5oz/yd.

Membrane can cut your overall weight down to .56oz/yd but after a decent coating it will be in the 1oz/yd range. I am doubtful that the extremely light fabric would do as well as DCF/cuben .51, though as far as overall usability. Durability will be way down with the DCF/cuben, but the weight savings would be about 2.5oz overall…it should weigh about 1.5oz without any taped seams. I think a minimum of 1.1oz/yd nylon (for strength) would be my choice for weight/durability/repairability/ruggedness/packing volume…it looks like the best combination of everything, assuming equal “weights” to all the variables. At two yards (assuming 3’x6′) it would weigh about 2.4oz (after seaming) plus about 1oz in coating. or right around 3.5oz. With bathtub, about 4 oz. Membrane would allow another ounce to be shaved off this (the base fabric), but would be weaker and prone to fussier/more delicate use. Both would be reusable after minor repairs and/or recoating (not something that is possible with DCF.) Weight vs ruggedness vs volume vs ruggedness, your trade off…

Polycro has the advantage of being fairly inexpensive. I think I say a window kit on sale at WallyWorld for 5.98 that was large enough for two ground sheets. Be carefull though, some is very thin… It is modular, meaning in dryer weather you can simply drop it.

Like Eric, I always fold the bottom onto itself, so I’ve never had a problem distinguishing which side is which. And like JCH, I use the heavy duty stuff, adds negligible weight and more durable. When things are stuck all over the bottom and shaking it isn’t working, I just find a tree (if I’m in an area with trees) and, holding each end, gently rub the bottom back and forth against a tree. Gets most of the crud off before folding and packing away.

I tried writing “upsidedown” but it wasn’t very helpful:

It was during the 2016 election, so I next went with the candidate’s names, but that didn’t help much either:

Oh well.

a man a plan a canal panama

okay, not mirror image symmetric but a palindrome

A man, a plan, a cat, a canal – Panama!

A man, a plan, a cam, a yak, a yam, a canal – Panama!

A man, a plan, a cat, a ham, a yak, a yam, a hat, a canal – Panama!

A man, a plan, a canoe, pasta, heros, rajahs, a coloratura, maps, snipe, percale, macaroni, a gag, a banana bag, a tan, a tag, a banana bag again (or a camel), a crepe, pins, Spam, a rut, a Rolo, cash, a jar, sore hats, a peon, a canal – Panama!

I stuck a small piece of duct tape  on each end and wrote “Up” on it. Also to help with folding I marked mid points with my sharpie.

Speaking of mirrored text, why do architects and draftsmen always label stairs with “up” and “dn”, which are perfectly, exactly, and always identical upside down.  Especially for architectural drawings, which are frequently viewed from all kinds of directions, what is wrong with these people??

To get back on topic, I’ve never used polycryo.

Edit:  Or is it polycro?  Guess it doesn’t matter…at least they’re both mirror-safe.

wow, amazing David,how can a palindrome be so long : )

Thanks for all the input. I won’t give up on polycryo just yet I guess. I will put my sharpie to work and see how it works out this hiking season!

Speaking of mirrored text, why do architects and draftsmen always label stairs with “up” and “dn”, which are perfectly, exactly, and always identical upside down.

Because Architects have a wicked sense of humor :)

I have a bunch of reflective dots I got for bike and helmet. I put a dot on the top of the polycryo so I can easily tell which side is up in the dark.

I get a lot of grief because I wrote “INSIDE” on the inside of my white Zpacks rain jacket. Some people sitting in the peanut gallery think I should have written my name or something more useful. But whenever I see “INSIDE” on my jacket, I’m not confused. I know it’s the inside.

and, you know it’s yours because you’re the only one that writes “inside” on the inside of your jacket : )

Emordnilap – Panama!

If anyone needs to pick up some cheap Duck brand window kits, Walmart is blowing them out.  I picked up two of the heavy duty kits (38 μM thick) for $2 and $2.50.  They were in the clearance aisle.  This will replace the Tyvek groundsheet I’ve been using under my Solplex.

Explain to me why  Polycro is better than 3 mil painters cloth plastic.

It doesn’t puncture near as easily and weighs slightly more. Like everything else, a trade-off.