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, The preparations did not form a gel except in the case of colophony: a non-flowing pale yellow material was formed after one day in the jar. The following protocols were used: Variation on the Original recipe of Gumtion ? Grind 1.2 g of resin (less than 1 min) in an agate mortar ? Add 1 g of Pb(OAc) 2 ·3H 2 O (s) and grind with the resin, Regarding the resins, we substituted the mastic with dammar (triterpenic resin), colophony, sandarac and copal (diterpenic resins)

, Add 2 g of linseed oil gradually (0.5 mL) and stir 2 g of varnish

, Add drop by drop 1 mL of a saturated solution of lead acetate in distilled water

, Sample (e) allowed to rest one night in darkness: the signal is more intense and apparition of a second radical specie, ? g)

?. , Mastic varnish (2.003 g) + Pb(OAc) 2 ·3H 2 O (0.505 g) + PBN (10.8 mg) ground 10 min : radicals detected, the signal is more intense

?. , The sample (h) is illuminated at 385 nm during 40 s: the signal is doubled, demonstrating a strong e ect of the light exposure on the amount of radicals. ? j) Mastic varnish (2.008 g) + Pb(OAc) 2 ·3H 2 O (2.003 g) + PBN (10.2 mg)

?. Pb, OAc) 2 ·3H 2 O alone does not contain radical species, even after grinding (a, b, c)

, Mastic varnish alone contain radical species, as described in the literature (d)

P. ?-when, OAc) 2 ·3H 2 O is added and ground in mastic varnish, the intensity of the signal decreases. The more Pb(OAc) 2 ·3H 2 O, the less radical species

, ? When comparing systems with the same amount of Pb(OAc) 2 ·3H 2 O, the longer the grinding, the more intense the signal. This could suggest an impact of the grinding on the radicals formation, but experiment (i) indicates a strong e ect of the light exposure

, Due to time constraints, we could not deepen these experiments