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The viscosity of naturally-occurring volcanic melts is a key parameter controlling magma dynamics and affecting the mechanisms of volcanic eruption. Although an accurate viscosity determination is crucial for unraveling magma behavior and related geological scenarios, determining the viscosity of pure and unaltered volcanic melts is not straightforward as these melts contain FeO, TiO2 and H2O and are thus prone to (nano)crystallization, volatiles loss and Fe oxidation when investigated by techniques such as ball penetration or parallel plate viscometry. To overcome this issue, differential scanning calorimetry (DSC) measurements are of fundamental importance as the dependence of the characteristic temperatures relative to the glass transition interval (Tonset, Tpeak,Tend) from the heating/cooling rate parallels the temperature dependence of equilibrium viscosity. Therefore, viscosity can be derived by applying constant shift factors (Konset, Kpeak, Kend) to DSC data. While shift factors are increasingly constrained for relatively depolymerized glass-forming systems, overall showing no significant dependence from melt chemistry, rhyolitic compositions remained relatively unexplored and some studies suggested that their compositional-related characteristics like the amount of excess oxides and agpaitic index may have a non-negligible influence on K values. This study combines DSC measurements at varying rates between 5-50 K/min-1 and ball penetration viscometry to accurately determine rate-dependent Tonset, Tpeak, Tend, low-temperature viscosity and shift factors of haplogranitic melts both pure and with varying network modifiers cations, analogues of evolved liquids such as peralkaline rhyolitic melts. Viscosity results are compared to previous studies and parametrized with available high-temperature viscosities. Further, Raman spectroscopy is used to thoroughly characterize vibrational and structural properties of glasses at Boson peak frequencies and the aluminosilicate region. Our shift factors are found to be only slightly affected by compositional variations and can be used to accurately retrieve the viscosity of natural silicic, peralkaline melts over three orders of magnitude using the DSC-approach.