In the last decade, Muizebelt and colleagues made important advancements concerning knowledge of the oxidative crosslinking of alkyd resins.[50-52] Fatty acids or fatty acid esters were used as model compounds to study the cross-linking reactions that occur under the reaction conditions of a drying alkyd paint, i.e. a thin film air-dried by a Co/Ca/Zr combination drier (see section 1.4.2) at room temperature. Ethyl linoleate autoxidation was monitored over an extended period of time (up to 1 year) using several analytical techniques.[50] In the oxidation of technical grade EL (composition about 70% EL, 30% ethyl oleate, traces of palmitate and stearate) followed by GC-MS it was observed that all ethyl linoleate had been oxidised in three days, while even after 110 days there is still some unreacted ethyl oleate left. The relative reactivity of ethyl oleate vs ethyl linoleate was determined using the saturated esters as internal standards. Both compounds decreased according to pseudo-first order kinetics and a reactivity ratio of linoleate to oleate of 17 was found, which has been reported earlier.[53] Size exclusion chromatography (SEC) showed relatively fast oligomer formation and the distribution of oligomers reached after one day did not change substantially upon further reaction. The peak assigned to hydroperoxides slowly decreased over time (up to 400 days), however. Discrete oligomers slowly disappeared, as was evidenced by a smoothing of the SEC curve after long reaction times. The formation of low-molecular weight material became more apparent over time. From these results it was concluded that cross-linking continues over prolonged reaction times with concurrent degradation.[50]