Questions about silk -washing & warmth to weight ratio.

Hand wash with a delicate detergent such as Woolite.

Insulation requires enough thickness to capture and retain air. Usually around 1/8 in thickness as a minimum. Silk is normally used as a baselayer to wick moisture from the skin’s surface, and it isn’t the best wicking material. Most people use a silk liner to keep the inside of their sleeping bag clean.

Silk does have some interesting properties for a single layer fabric, but as Nick outlined, you need a certain amount of thickness/loft before you can still air more efficiently for any noticeable conductive and convection based insulation.

Apparently some early, pioneer teams climbing Everest used alternating layers of silk and wool to working effect, but we’re talking multiple layers, and the wool + many layers helped to add loft/thickness to the system.

Anyways, when you’re looking at fibers and their potential to be good thermal heat energy exchange resistant materials–you’re looking at a few different things with relative importance.  First and most important by far is size and number of fibers per given volume.  Thinner/finer fibers and more per given volume are better at stilling air than larger and less numerous ones.  One of the reasons why high quality goose down is so good.

Fiber shape. Perfectly round or flat fibers, are not as good at stilling air as more shaped ones.  In silk’s case, the fibers are trilobal in shape i.e. fairly 3D triangular in shape.

Then the fibers or insulation’s actual material, and it’s degree of thermal conduction, or rather lack.  Silk, being a protein based fiber, is more thermally resistant to conduction than many other fibers, though I don’t remember seeing specific numbers for it like some of the others.  But this is less important, especially in lofted materials, than the 2nd, and especially the 1st factors.    I don’t know what exact percentage each variable plays a part, but fiber size/amount is definitely the majority of the pie of the 3 main variables.

There is also potentially IR factors, but this is even less than the 3rd, and I think most materials commonly used for clothing, are somewhat IR transparent (?  This is kind of a complicated subject because the IR range is pretty wide, and different materials are more absorbing, emittive, or reflective at different wavelengths along that wide spectrum. So it’s kind of hard to over generalize.  One thing that we can overly generalize though, is that only very smooth, shiny/reflective, metallized film type surfaces are very good at reflecting broad range/spectrum of IR).

So if one wanted to create a slightly warmer per weight and volume, single layer fabric for say a baselayer or sleeping bag liner–something that would be more ideal than most, would be using a combination of medium sized, hollow polypropylene fibers, woven with finer (microfiber) pp fibers, and both more shaped (i.e. not perfectly round nor flat), and then with a thin, reflective, metallized Al coating on the outside to reflect IR.

If you get all the variables completely right and in balance, you might notice a slight difference between a typical baselayer or liner fabric, and such a proposed fabric.  But it’s really going to be barely significant.  At most, maybe a couple to few degrees per similar thickness.  Why PP?   Pretty low density, pretty cheap, decently strong and durable (when woven), and pretty low thermal conductivity relative to other commonly used fiber materials.  Metallized coating to reflect IR at a broad spectrum/range.

Or to more simply and quickly sum it up.  Silk might be a degree or couple degrees warmer per single layer of similar thickness fabric than some others, but it’s not enough to really matter.  Liners are less for warmth, and more for cleanliness.  The proposed, more ideal fabric outlined, would likely feel a bit warmer than even the silk, but again, in a single layer–not going to really matter too much.

With that said, I’ve had the thought that a silk/wicking polyester or silk/wicking polypropylene blend, would make for an interesting baselayer fabric.  Silk lowers the stink factor and increases comfort factor some, while being tougher, more comfortable, and more durable than sheep’s wool and not quite as water holding, and the polyester or polypropylene to speed up drying time, decrease price, and increase strength and durability.

Another interesting blend would be alpaca with wicking polyester or polypropylene. For similar overall reasons.

(On the flip side, for coolness in hot conditions, blends of flax linen with wicking, microfiber and/or flat shaped nylon, would be slightly better than most of what’s out there).

Note regarding my nylon recommendation in the above… I seemed to have contradicted myself and the outlined principles by specifying microfiber nylon to help with creating a more cool fabric.

I said that, because I remember reading some research which indicated that tests with certain size microfiber nylon was more IR transparent in the human range than a number of other materials tested.  If it allows our IR to flow out, it could be potentially more cooling in nature despite the microfiber size. The trick is to also make it rather air porous (just tight enough to block UV and visible light sufficiently), so it’s also not good at stilling air.