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This paper presents a protocol for safe quartz etching with hydrofluoric (HF) acid as part of sample preparation for luminescence dating. Concentrated HF is extremely hazardous and can cause severe burns and poisoning, even leading to death. Generally, in order to avoid exposure to light and bleaching, HF etching is performed in a dark laboratory under weak orange-red light in wide-open beakers. Handling HF in open beakers in the dark could result in unfortunate accidents due to unintentional spillage. The presented protocol avoids these two main safety issues - working with open beakers and under poor lighting. The samples are etched inside black opaque bottles with narrow openings so that the procedure can be safely performed in comfortable light levels. To validate the harmlessness of the laboratory environmental light, bleaching experiments of quartz were conducted under the same conditions as the protocol. These showed that no bleaching occurred during this procedure. [ABSTRACT FROM AUTHOR]

In the past years much research has gone into developing luminescence methods that can reliably date samples older than what is possible with quartz OSL, into the Middle and Early Pleistocene. Quartz OSL is limited by signal saturation in the range of 100-200 Gy. The benefits of later signal saturation of the extended range dating (ERD) signals are often hindered by slow bleaching in nature or by thermal instability, rendering these signals less useful in some sedimentological settings. Selecting the appropriate mineral and signal depends on the expected age, available minerals, their signal intensity and depositional environments. We explored the most commonly used extended range dating signals in fluvial and aeolian sediments from Israel. In aeolian sediments, prehistoric sites and sequences of paleosols provided rough age constrains, and in fluvial sediments -- terrace staircases with age estimates based on elevation above current channel and reg soil maturity. The thermally transferred OSL (TT-OSL) signal of quartz, the post IR-IR signal at elevated temperatures (250°C or 290°C) of alkali feldspar, and violet-stimulated luminescence (VSL) on quartz were compared one to another in different depositional setting, allowing insights and conclusions about their suitability. We also tested these signals on late Holocene samples that appear to have been well bleached at the time of deposition, as attested by the small errors on the OSL ages, to estimate the residuals of the ERD signals under common depositional conditions. For coastal sands and fossilized sand sheets and dunes, the alkali feldspar pIR-IR250 signal provides ages that are about 30% lower than the pIR-IR290 ages. Correcting to fading does not bring the two sets of ages in line. However, there is a very good agreement between the quartz TT-OSL and pIR-IR290 ages, supporting their reliability. With low dose rates, ages of up to 1 Ma can be achieved with both signals. As for fluvial sediments, comparison of the OSL ages with the pIR-IR250 ages shows that, within the reliable range for quartz OSL, pIR-IR250 provides useful if somewhat older ages, most likely due to slower bleaching. On the other hand, the TT-OSL ages are as much as 200 ka older than the OSL ages, attesting to the poor bleachability of that signal in fluvial environments. The VSL signal proved to saturate as early as the OSL signal, and at least for the studied samples, is not suitable for ERD. In late Holocene fluvial samples, the TT-OSL signal overestimates the OSL ages by tens of thousands of years, however in aeolian settings the pIR-IR ages are in fairly good agreement with the OSL ages. Thus, it is advisable to test different ERD signals in modern sediment samples before choosing the most appropriate signal. [ABSTRACT FROM AUTHOR]