## 2 Materials and Methods  
### Wood Material and Test Samples  
Three types of oak wood material, namely subfossil oak (SO), aged oak (AO) and recent (new) oak (NO) were employed in this research. The SO material originated from three buried trunks (S1, S2, S3) accidentally discovered in riverbeds in three locations in Romania, as presented in Figure 1, alongside their GPS coordinates. The SO wood material provided to our faculty for testing was in various forms: air-dried timber pieces (S1, S3) or crosscut log sections (S2). Two such pieces (100 mm thick discs), one cut from the base of the trunk (S2a) and the second cut at 6 m height from the base (S2b), were investigated. Wood elements recovered from constructions on the occasion of their demolition or rehabilitation were used as sources of AO material. There were two elements (C1, C2), namely a beam and a pillar from the traditional porch of a house built around 1930 in Valea Mare-Bratia, Arges County and one beam (C3) from the roof structure of a house built around 1970 in Codlea, Brasov County. An approximate age of 90 years in the conditions of use class 3 (UC 3) according to [30] could be considered for AO_C1-C2, while 30 years in service in UC 2, followed by 25 years storage in conditions of UC 3+ (outdoors, covered, near soil contact), should be acknowledged for AO_C3. Four pieces of recent oak timber (50 mm thick) from the workshop of the Faculty of Furniture Design and Wood Engineering were employed as NO material for comparison.  
Prismatic test samples with dimensions of (30 \(\times\) 20 \(\times\) 20) in (mm \(\times\) mm \(\times\) mm) on the (L \(\times\) Ra \(\times\) Tg) directions were prepared by careful mechanical processing from the air-dried wood material of all the presented assortments. This type of samples was employed in this research to determine all the selected physical and mechanical properties, namely density, coefficients of swelling and shrinkage, and the compression parallel to grain.  
Depending on the form of the available material (timber pieces, wooden log cross sections, elements recovered from constructions), adequate processing phases and cutting schemes were applied (Figure 1). Special attention was paid to preliminary cuttings to remove all obviously degraded material (AO) and/or sapwoodby-case basis. Then, cuttings in the radial direction were carried out to ensure obtainment by further adequate processing of intermediary baguettes (scantlings) with cross sections of 20 \(\times\) 20 (mm \(\times\) mm) in the Ra and Tg directions, respectively. The annual rings were parallel to one of the cross section sides. The final test samples resulted from crosscutting at 30 mm length the longitudinal direction.  
All the samples were coded and numbered during the whole mechanical processing steps so that their location in the original material could be clearly understood and traceability ensured. Numbering of the intermediary baguettes/scantlings started from the bark/outer part of un-edged timber inwards. The first two scantlings were considered sapwood, while heartwood was considered from scantling four inwards. Core wood (pith) was eliminated (when present) in all cases. Only samples following standard conditions were used for testing.  
The codes of the sample series corresponding to the three types of oak wood material (SO, AO, NO), respectively the seven different assortments, alongside the total number of samples investigated for each assortment (mentioned as figures in brackets) were as follows: SO_S1 (37), SO_S2a (35), SO_S2b (37), SO_S3 (32), AO_C1_C2 (63), AO_C3 (43), NO (64).  
Figure 1: Types of wood material and phases of test samples preparation: (**a**) log cross sections (SO_S2a, SO_S2b), (**b**) timber pieces (SO_S1, SO_S3) and (**c**) elements of aged wood recovered from constructions (AO_C).