To be a Silkweaver Mistress its required to have been a Silkweaver for 10 years, being an Arano, female and have a working spinneret. The quality of the silk of the spinneret must be spotless.
After this 10 years of excelent work, a weaver has to prove their worth to a mistress. If the Mistress likes her work, she takes her up as an apprentice. After 5 years of learning, the trainee has to make a masterpiece and present them to a gathering of all the Mistresses of the province, if they deem her worthy, she becomes one of this select group.
Payment & Reimbursement
A Silkweaver Mistress can sell the already expensive silk at much higher prices, making her eventually one of the richest members of Aracno society even if she was born very poor.
Also, a Mistress is a very valuable member of society and play a high role in politics, as not all villages have one, and only really large cities have more than two. Having a Mistress is really a motive of pride or prestige in any village ruled by the Aracno.
As any other weaver, spinning wheels and looms are a must have.
A Silkweaver Mistress worth of her name only use her natural silk to produce their work. If a Mistress was found working with the silk of another Arcano or worse, another kind of arachnid she would lose all the prestige and the tittle inmediately.
Other than that, Silkweavers in general use all kind of dyes to give color to their fabrics.