**1. Introduction**

Foraminifera shells (tests) are widely used in paleoceanographic and paleoclimatic studies as biostratigraphic or ecological indicators and through physicochemical analyses as proxies of past oceanic conditions [1]. The tests of different foraminifera species can provide environmental information by means of both physical and chemical analyses. Despite the main focus for environmental reconstructions based on stable isotope [2,3] and trace metal geochemistry [4–6] of foraminifera tests a wealth of information can be attained by their physical analyses that include the study of shell fragmentation [7], abundancies for ecological [8] or biostratigraphic purposes [9] and shell biometry [10–12] including size [13,14] and weight [15,16].

A necessary preliminary step for the use of foraminifera tests in paleoenvironmental studies is the isolation of the test specimens from the muddy sedimentary matrices, that consists of several components. A number of methodologies have been employed to transform the bulk sediment samples into useable micropaleontological material [17,18] as a first level treatment. Although the additional cleaning protocols to isolate primary calcite for geochemical analyses are advanced and several cleaning experiments have sought to quantify the effects of each of these methods on measured elements [19–22], there are only a few studies that assess the efficiency of different treatment procedures on the physical properties of the foraminifera shells such as their weight [21,23].

Studies that focus on foraminifera shell weight measurements are particularly vulnerable to the degree of test contamination, due to their foraminous nature, these specimens have the potential to include contaminants (i.e., sedimentary residuals), which can alter or skew the record toward heavier values [24]. Residual clays or nano-ooze in poral spaces and shell surface obstruct the study of test ultrastructure that yield information about the degree of carbonate dissolution [25] or test porosity [26]. Furthermore, such coatings or infillings (in apertures) often precludes automated recognition software, which is based on morphological features of foraminifera shells [27], from classifying their images correctly [28] and greatly complicate specimen segmentation when using high resolution X-ray tomographic techniques [29]. In the present study, by using light microscope imaging, SEM and X-ray tomography to assess the cleanliness of tests treated with reagents that are established not to alter the fossil geochemical signal, we propose a methodology that effectively diminishes surface and internal specimen contamination.
