What we mean when we choose a hemp blend over a polyester tee

Two materials, not a moral score

Polyester is a synthetic fiber. In ordinary speech that is what people mean by a plastic tee. Hemp is a plant fiber. Batch 01 uses hemp in a blend. We do not print a percentage until the factory confirms the fiber in the goods we are selling. Research we cite below describes hemp textiles in general, and one woven hemp cloth in particular. It does not describe a Symbiosis Air Weave tee.

Choosing the blend is a systems choice before it is a comfort claim. A shirt is a small daily object tied to a field, a mill, and a wash cycle. We want that chain to start with a plant fiber we can name honestly. We do not treat hemp as a fix for every problem in clothing, and we do not ask anyone to feel ashamed of the polyester they already own.

What the hemp study actually measured

The study in this draft is Grifoni and colleagues, 2009, Photochemistry and Photobiology, file Photochem Photobiology - 2009 - Grifoni - Laboratory and Outdoor Assessment of UV Protection Offered by Flax and Hemp.rtf.

They tested woven flax and hemp, undyed and dyed with natural dyes, in a lab and outdoors in Italy. Protection depended on the cloth in front of them: fiber, cover, weight, thickness, and dye. Their undyed hemp was 173 g/m² and 0.67 mm thick, with a cover factor of 96.2%. That is a fairly tight woven cloth, and it still was not a sun shirt. Outdoor UPF was 5.8. In the categories they used, good protection starts at 15.

In the lab, that undyed hemp let through about 12% of UV at 296 nm and about 22% at 396 nm. Dyeing changed the story when the cover was already high. Outdoor UPF on their hemp ran from 5.8 undyed to 29 on the weld dyeing, which they class as very good. Other hemp dyeings, except cochineal, also cleared the good-protection line outdoors. In the lab, the better hemp dyeings (not cochineal, brasilwood, or lipsticktree) landed between UPF 16 and 19, and the lab number was generally the lower of the two methods.

Read that as a guide, not as our spec. Undyed flax, cotton, and hemp were not perfect UV filters in their discussion. A different weave, a knit, a lighter weight, or a pale dye can miss the line their darker hemp dyeings reached. Our tees are not those swatches. Batch 01 has no UPF test. We will not print one.

Where polyester already does a job

The same paper's introduction, drawing on earlier studies, says synthetic fibers such as polyester can offer good protection from UV, and that they are water-repellent and therefore uncomfortable to wear in high heat. We keep both halves. A polyester tee can be the better sun cloth. It can also feel wrong on a hot day because it does not take water the way a plant-fiber cloth does. That is a materials note. It is not a verdict on the wearer, and it is not a breathability score for our blend. We have not measured air flow, dry time, or heat on Batch 01.

So a scoreboard is the wrong picture if it means hemp wins every column. We are not claiming a stronger fiber, a lifetime garment, or a medical benefit. We are not claiming that our shirt sheds less in the wash, blocks more sun, or stays fresher. Those tests are not in this draft.

What we will say instead

• Batch 01 is a hemp blend for everyday clothes: the Men's Air Weave Tee, style TBD004, at $44; the Men's Boxer Shorts, style TBD001, at $30 (three for $81); the Women's Boy Short at $32; and the Drawstring Short at $64. Those four are the first checkout styles.
• The Hemp Work Pant and the Men's Hemp Hoodie, style TBD002, are waitlist prices at $108. The Men's Structured Hemp Jogger, style STY00002, is a waitlist price at $128.
• Shipping is free at $88. If a style misses its factory minimum, the draft policy is a full refund. That is draft policy, not legal advice. There is no lifetime warranty.
• Photos stay off the product page while the frames are not approved.

The reason to choose the blend is the one we can already mean. You get a plant-fiber blend, named without a fake percentage, from a batch that shows its unfinished tests. When the factory confirms the fiber, and when we have washed the finished cloth, we can add the next lines. Until then, a quieter sentence is the accurate one.

The same draft is stored as markdown. The shelf and the test log are on the Batch 01 spec sheet.