In this poster I will present the cumulative work (Specker et al., 2018; Specker, 2021, Specker et al., under review) done to develop and validate the Vienna Art Interest Art Knowledge (VAIAK) Questionnaire. The questionnaire was developed to address two problems in the field: a lack of conceptual clarity of what art expertise is, and a lack of coherent measurement for assessing expertise. The VAIAK addresses this by focusing on the measurement of two commonly studied sub-domains of expertise: art interest and art knowledge. It consists of two separate scales, one that measures art interest (11 items) and one that measures art knowledge (6 multiple-choice and 20 open answer items, 26 items in total).In the paper I will present evidence that supports the psychometric model of the VAIAK (by way of CFA), present validation evidence in terms of concurrent and discriminant validity, internal structure (reliability), discrimination ability (between experts & non experts), configural measurement invariance, test-retest reliability, and most recently an item-focused perspective using IRT as well as qualitative analyses. This research has increased insight into the workings of the scale and led to a modified version the VAIAK-R. Beyond specifically discussing the VAIAK, I aim to show more generally how continuous validation efforts of any scale could look like and what theoretical as well as methodological insight such research efforts can provide by using the VAIAK as a case study.