I happen to have bought a French & uk magazine recently both of which carry an article on Albarracin.
The French article is very clear that the access situation is fragile & gives a list of rules which must be followed in order not to jeopardise this.
Quite high on the list is visible marks so no tick marks & an absolute minimum of chalk.
The British mag, by contrast, mentions chalk only in passing within the tesxt, without empahasising it's importance & has a set of picture in nearly all of which chalk bags are being worn.
So I had a look at
http://www.boulderalbarracin.com/topoalbarracin.pdf
where it again gives a list of rules & no 4 is:
"4.- Minimizar en lo posible el impacto visual del magnesio en la roca, utilizando el minimo imprescindible, o mejor, usar
eco-magnesio (con tinte similar a la roca) y cepillando/trapeando el mismo tras su escalada, así como no esta permitido
hacer clecas.y en el caso de que ses estrictamente necesario, colocar tritas de espadrapo que luego seran retiradas."
Now my Spanish isn't great (anyone care to translate) but it seems clear that minimizing visual marks is highly important.
