What is the length of string for your bow?
In Archery, the Technical Side, Maurice Taylor has an article on bow strings written in 1940. Much of the focus was on linen since it was the primary bow string material at the time. He investigated the affects of moisture and wax. The linen he tested showed as much as a 50% increase of strength with the addition of moisture over dry string. The best strength to weight occurred when the string had a 9-10% moisture content. So if you are in a dry climate, it will greatly improve the strength of the string to keep it slightly moist. Just 9-10 grains of moisture added to a 100 grain string is about perfect. My experience agrees with this. When I am using a bow with a linen string at a very low humidity place like the Bonneville Salt Flats, then I periodically wipe down the string with a lightly dampened cloth and this has worked very well.
In Maurice’s article, Taylor also tested the effects of adding wax to the string using a number of methods. The effects on strength was the same or worse than without wax, but the wax added weight reducing performance. It is interesting that your wax string seems to be holding better than the non-wax.
Barbours pure flax sinew is often really good. It was probably last manufactured in the 1970’s, but I have a ton of it and have no trouble getting it. Just make sure you to avoid any labeled as “soft”. I often use a thin 4-ply which I tested with a breaking strength of about 28 pounds dry. I figure a 64” long string for a 58 pound bow would weigh about 90-100 grains fully served with silk and with reinforced loops.
There are also current linen thread suppliers that are about as good. I can send you a list.
Steve, how does the linen you get compare to the pure flax sinew?
Alan