Flying the Tartan (No, not a "fly plaid")

[Todd Bradshaw]

In the sailmaking and boat cover business the most UV and weather resistant fabrics we use for boat covers and such tend to be acrylic first, followed fairly closely by polyester. It's not unusual for good ones to have a warranty to withstand five years or more of constant exposure without sun rot (the sun is usually a much bigger danger to these fabrics than water, as long as they have decent ventilation so that they can dry out after getting wet). The dye used to color them might be a different story though. They may or may not fade badly, and I don't know how you might predict the results for fading for fabrics not specifically designed for outdoor exposure. Most of the marine fabrics these days are pretty colorfast. Tartans not really intended for that sort of use? Who knows?

One thing you can do though is to routinely treat the fabric with 303 Fabric Guard (pump spray squirt bottle available from places like Amazon - not cheap, but excellent stuff). Fabric Guard is not only a water resistant treatment, it also contains the best UV absorbers that you can buy, and that's what is going to help reduce fading and sun rot. Basically, the UV blockers convert UV to heat, where it can dissipate into the atmosphere, rather than deteriorate the cloth. Over time, they get used up doing their work, so periodic re-treatment is a very good idea.

It won't alter the color or look of your fabric, but can have a big effect on water absorption, fading, and UV life in terms of tear strength. Most fabric projects are better off when well protected from both being regularly soaked and exposed to the sun.

Egyptian Cotton sailcloth samples with no treatment and Fabric Guard treatment.