The primary condition of a dendrochronological analysis is that on the sample which was intended to be analysed there are present at least 31 measurable annual rings. The sampling basically can happen in three ways: on the place of occurrence with drilling, or taking external measurements ourselves, or by posting samples for those who are interested in such kinds of analysis.
I. In the case of researching monuments we take a sample from the wooden structures with a special drill bore-hole.The diameter of the hole in case of oaks is 20 mm; in case of fir beams 25 mm. In this way the sampling does not affect the statics of the elements and structures. In case of replaced or changed elements we saw off a slice to be able to measure the annual rings along more radii. From a contemporaneous wooden structure it is appropriate to take at least 6 samples in case of oaks and 10 samples in case of the different fir-trees; but if there are replaced elements in the structure or indications of reconstruction, then, obviously, more samplings may be needed. Taking samplings from historical buildings or monuments in the interest of the documentation and the correct evaluation, basically we do ourselves on the spot.
II. In the case of wooden works of art drilling is not possible, naturally, that is why in these cases with a
method which causes no destruction we measure on the surface of the object the width of the annual rings. We do the measuring after the cleaning of the surface with a digital microscope-camera or with a hand-operated scaled magnifying glass, and then the data is digitalised in the laboratory later. With this method we can define the exact chronology of panel paintings, altars, coffered ceilings, choirstalls etc.
III. The collecting of archeological samples needs the contribution of an archeologist. Depending on the condition of the wooden relics at the location we ourselves cut, saw or drill the samples. But most often the leading archeologist of the excavation posts us the carefully wrapped, wet or charred pieces of wood. In the case of stakes or beams to be measured it is enough to have a slice of 2-3 cm thickness, and in this way sufficient control samples will remain at the source location or in the museum. For the successful investigation of charred wood it is only possible if the samples are of adequate size; they contain enough annual rings and they must have been wrapped sufficiently carefully to arrive at the laboratory in a condition in which they can be accurately measured.
In the dendrochronological laboratory we prepare the transverse section of the area of the samples and we carry out the definition of the tree species. This is followed by the measuring of the annual rings to within one hundredth mm precisely on a special measuring table with the help of computer programmes which were developed for this purpose. The dating of the annual ring series obtained through this measurement is done by comparison with the dated Transylvanian and foreign chronologies. The dating in all cases refers to the time when the tree was cut out!