I agree. Any dealing with the artifacts, no matter how 'delicate' the act is, interferes with the original status of the object. This would affect the longevity and condition of the object even if we did not think so. The potential damage is maximized when dealing with organic objects such as human remains, mummies, papyri.

I support removal of such a term 'non-destructive' to ring a bell that in each time we deal with the object, there is a potential for damage.

Hi Sahar, In my original question I accentuated NAA and petrography. I am sure that you sealing with CT and X-Rays in general must have asked yourself what the X-rays will leave behind on an artifact. I remember van Gogh's painting which was tomographed and another of his paintings was found beneath the existing one. I am afraid that in the future curators will not any longer allow to do this type of work because in spite of what good comes out of the results, the sampling/analyses are really damaging and cannot be restored..

If we use the term 'less-destructive' the curator wil ask questions before she/he allows to perform the analyses.

Sampling is not destructive only in the case where your sample comes from an area that is already broken and there is no hope that the sample can be placed back in its original position.

There are however non-destructive techniques, i.e. non-destructive portable XRF. All you have to do is put thhe machine in front of the object-no sampling required.

Hi Evangelia, even when a sample comes from a broken pot, a shard, and even when it is taken from a place that nobody will ever see. it still is destructive.

Even your handheld portable XRF has to give off an X-ray in order to get a secondary X-Ray back that can be calculated and provide results. The XRF emitter IS damaging, even when you can't see it on the moment.

Correct. Then we reach a point where we have to discuss up to what point can destruction be considered acceptable, and place limits into the needs of analysing artefacts. How necessary is it really to analyse? Can our scientific curiosity be excused in all cases? In Greece there are instructions on how to sample. You have to do a lot of paperwork before you are allowed to take samples and analyse. The rule is to justify why your analysis is needed, and only take small samples from areas that are already damaged and that the sample is considered impossible to be placed back in its original place by conservators anyway.

Evangelia, yes, of course, there are questions of how eminent is the urge to analyze Cultural Heritage materials and do we really have to know the conclusions as a result of our analyses.

It is good that there will be red-tape because otherwise there won't be any supervision, also if we don't like it so much.

We would have to look for techniques that are less invasive than others and choose these ones.

However, we should use the term less-invasive instead of non-destructive methods, because as said earlier, every analytical technique is less or more destructive than another.

Dear all!

We use for the non-destructive investigations of stones in medevial and antique objects and buildings the classical optical methods with magnifying glasses supplemented by a portable XRF and sometimes ultrasonic measurements.

Of course you need a lot of experience and a relevant data-base to get meaningful results.

best regards

Andreas

Andreas, yes you are right that stone can be analysed by using magnifying glasses and portable XRF. Splendid for stone that will not suffer very much by such analyses.

But what if you do that on parchment or on a drawing? The magnifying glass is not providing the requested information, whereas XRF portable or stable will damage the objects. XRF measured secondary X-Rays that return from an item after having been bombarded by primary X-Rays and the latter--irrespective how large the bombarded area--is not and will not beneficial for the artefact. Whether science has to stop or continue to work with X-Rays or even Gamma-rays is another question.

I am of the opinion that sometimes--when it is really needed--one must analyze by destructive sampling. Getting results by virtual sampling is as yet impossible, hence my first remark that the term non-destructive sampling is obsolete

I think we should make a difference between sampling, materials and techniques when talking about non-destructive or non-invasive.

Taking a micro-sample on an artefact is invasive and destructive, while its analysis can be non-invasive and non-destructive. Also, the difference between invasive and destructive should also be taken into account. Invasive means that there is an interaction between the material and the technique, while destructive means the material is destroyed = cannot be re-analysed.

Based on that, some techniques are invasive, but non-destructive.

Also, semi-invasive techniques do not exist (at least in my opinion), while semi-destructive techniques exist. A preparation technique, such as cross-section for example, is semi-destructive. During preparation, part of the sample is polished = destroyed, but the rest of the sample remains whole and could be re-analysed (extraction from resin can be discussed). We can argue about how much invasive this preparation is then, but it largely depends on the method of preparation/protection.

When the cross-section is analysed under an optical microscope, the destructivity depends highly on the material we are observing (exclusion of staining). For most cases (hard substrates, inorganic materials, resins, some organic materials as well), it is non-destructive and non-invasive.

When SEM is used, the same principle can be applied, which means we will have a non-destructive, but invasive analysis. Again, it depends on the material analysed.

In conclusion, the terminology should be carefully explained, and what is determined as non-destructive, semi-destructive, destructive (same for the invasivity) should be carefully described.