Tip:
Highlight text to annotate it
X
Hi my name is Evelyn Ayre and I am Conservation Intern from Queen's University in Canada.
Today I'm going to talk about our lovely Bruker M1 Mistral XRF machine that is X-Ray Fluorescence machine.
And I will talk to you a little bit about the theory behind XRF.
So when we use this XRF machine what is happening essentially is that this machine will fire a beam of x-ray radiation
at the object that we choose and on an atomic level what happens is
the electrons that are close to the core of the atom are excited and ejected out
and the outer electrons of this atom will compensate for this loss by dropping down to a lower energy level.
And when this happens the electron because it is dropped from a higher energy level to a lower energy level
will release some energy in the form of a photon basically.
When we use this machine effectively what is happening is that the machine is reading this ejection of energy that is produced by the electron dropping down.
So first step when we use this machine is to do a calibration for the machine of a known standard
so in this case we use a silver calibration which is a known percentage of silver
and this is used to calibrate the compositional analysis software which allows us to then determine what percentages
of different elements are in whatever objects we are testing.
So it improves the accuracy and precision of what we are measuring.
So here we have our known standard and we are going to use silver which is right here.
And then we raise the platform so that the object is positioned at the right level for the x-rays to be read.
Okay so now what I am going to do is actually take a measurement of a bit of gold on an object that I recently conserved.
This is K1010 and I am interested in seeing what the composition of the gold of the filigree
as well as the gold sheet at the back as well as perhaps some other areas on it.
But I am going to start with the gold sheet first.
So here what I have done is I have placed the object in the machine and on the screen here you can see the object
the area we want to measure is in focus and we have the crosshairs indicating where we going to be taking our measurement.
So this is the spectrum that is produced by the x-ray fluorescences.
So what we can see from this spectrum is that the machine has figured out the composition of this gold sheet that we have tested.
It is a 21 carrot gold.
It is made of almost 88% gold there is about 7% silver and about 4% copper.