17th Century Modern Materials

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The six samples as they were given to me – these are nice big samples too, sometimes we get ones much much smaller!

A while back I was given six small samples to analyse – nothing unusual about this till I looked at the images of the object that the samples had come from and immediately had grand notions of treasure hunting for the Holy Grail with Indiana Jones! These thoughts were soon followed by me humming ‘knights of the round table’ down the back of the lab…

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17th Century cup (Museum no: 659-1904). On the right hand side of the image you can clearly see on segment that had a number of different cracks – I also think the cup looks like something from Indiana Jones… (c) Victoria and Albert Museum, London.

We do a lot of analysis of this type in the lab – a conservator will come to us looking to identify the materials used in a past conservation treatment. In this case the amber cup had been treated a long time ago to join the broken sections back together. Depending on the type of material used, the length of time since the treatment and the storage/environmental conditions, old conservation treatment can be in various conditions. The material used in the previous treatment of this object had become discolored and was also beginning to fail; the joints were starting to crumble away. This impacted the object in two ways – the failing joints meant the cup was structurally vulnerable and the discoloration impacted the interpretation of the object.

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This image shows where the conservator took samples. They are all along joint lines, where the adhesive is failing and where samples were easily taken. (c) Victoria and Albert Museum, London.

Now you might be wondering what the intern for modern materials is doing anywhere near an object from 17th century Prussia! When we analysed, via FTIR, the samples they mostly turned out to be amber (shocking considering the cup is made from amber and is also is used in conservation treatments) and some pigment (probably burnt sienna).

Image of one sample under magnification, showing what looks like two substances joined together. The red substance is most likely burnt sienna, while the glassy substance was amber

Image of one sample under magnification, showing what looks like two substances joined together. The red substance is most likely burnt sienna, while the glassy substance was amber. (c) Victoria and Albert Museum, London.

The main issue with FTIR, the scientific method we use to identify materials of this kind, is that in the resulting spectrum we see everything that was present in the sample. I spoke a little about FTIR in a previous post but didn’t delve in the world of mixtures.

If we look at the image below of two spectra from the same sample we can see that they don’t quite match up (don’t mind that the peaks have different heights this could be due to other issues like thickness of the sample used) . There are a few extra peaks in the Blue spectrum compared with the Red.

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Spectrum from different area in same sample showing the sample is a mixture. The peak at 1 has a larger shoulder in Blue than in Red; A peak at 2 is found in Blue spectrum and not in Red; The ratio of peaks at 2 &3 are different in Blue than in Red; Formation of new peaks at 4 and 5.

One of the easier ways we can try and distinguish mixtures is to subtract one spectrum from the other using computer software. This method isn’t perfect and a certain amount of skepticism is required – luckily this particular mixture was very straight forward. The image below shows the resulting subtraction in Red. The Purple and Green spectrum are the closest matching spectrum from our database; both are aged Cellulose Nitrate.

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Top spectrum (in red) is resulting subtraction. The two other spectra are the nearest match from the database. Both of the nearest matches are from aged Cellulose Nitrate.

Cellulose nitrate was the first semi-synthetic “modern material” to be produced and mass marketed. In the beginning it was mostly associated with shirt collars and cuffs, and then later with film negatives; it was also used in conservation treatments and industry. However, it has a tendency to discolor, disintegrate and spontaneously catch on fire. Outside of traditional objects we commonly find cellulose nitrate used as a protective coating and adhesive in past conservation treatments. The issue conservators have is with their removal as sometimes one needs to used harsh solvents – this could have implications for the object material. The manner in which cellulose nitrate degrades can also affect the object as nitric acid is formed and this can speed up the decay of surrounding objects.

Mini post No. 10 – How to scare the intern…

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Though my university training and this internship I have come accustomed to handling museum objects, and for the most part I’m perfectly comfortable doing this – except when it comes to the ceramics study galleries. I’ve always loved those new galleries but they have always scared me a little – something about densely packed fragile ceramics in-cased in glass just make me nervous. If you’re planning a trip to the museum do go and visit them, its spectacular to see all the collection in one place.

Yesterday we installed some newly calibrated OCEAN monitoring unis, the environmental monitoring system used in the museum, in the display cases which means reaching in to take the old one out and reaching back to put the new one in. Normally the curator of the relevant gallery case does this, but yesterday I was allowed to place the ‘easy’ one onto the shelf. The more difficult ones, the units hidden in back behind all the lovely highly breakable ceramics, were done by the curator. I just closed my eyes at this point, hoping we didn’t start the worlds most expensive domino falling world record attempt!

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The easy monitor to put in place – not too high up, not close to anything that can break and easy to get to! On a side note, if you ever went to a museum and wondered what were those weird looking things in the display cases chances are they are for monitoring the environment.

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The difficult one… on the second highest shelf, right at the very back of the case, as close to the edge as you can get and right beside really fragile objects! Not to be replaced by the faint-hearted!

Raspberry Pi Project – 1st video

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Last July I wrote about our project using a raspberry pi and its camera module to track the decay of a plastic handbag. The project has been running for about 4 months now and we complied the first video not so long ago.

To be honest we were more than a little nervous about this project, as to us, little if anything had happened for the majority of the summer, but as the seasons changed a few things started to happen!

So a number of things are pretty clear from the video – the major one being that it’s not as dramatically catastrophic as we had hoped! Ironically the video doesn’t pick up on the areas most changed – like the great big hole on the lower left side that is blocked by the beehive bag, nor does it pick up just how many crystals have formed as they are mostly on the sides. The second is that the limitations of the camera module mean the resolution is low – but for a £25 camera it’s still good enough to give up some great information.

The sides of the bag have had seen a large formation of crystals over the three months

The sides of the bag has seen a large formation of crystals over the three months

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The large crack on the bottom edge of the bag on the left side of the image (proper right of bag) is not seen forming on the time lapse as its photobombed by the edge of the beehive bag

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The beehive bag, which I’ve talked about before, is still falling apart! Originally one side broke apart faster that the other, now that ‘better’ half is breaking up. The main crack in the bottom of the picture was only a hairline fracture at the start of the timelapse.

If you look at the video closely you will notice two things of real importance. Firstly, each of the cracks that were present at the start have gotten a little bigger and the delamination of the bag is wider. Remember that we are looking at two months data over a 3 month period, so for things to get noticeably bigger in this timeframe is a real shock in a museum environment. The second thing to notice is the way the cracks grow. If you look closely at the top right corner of the bag you will see the shadow and highlights expand and contract. We also see the beehive bag expand and contract. This might be due to the environmental conditions of our science lab and could be what is ripping our bag apart.

Our next job is to try and improve the video quality and also relate the visual information gained to the data from our environmental monitoring system. From this we may be able to come up with an insight into the storage of plastic objects.

Mini Post No. 9 – Sometimes we get things wrong!

*NOTE – So the lovely people in the media department at the V&A have asked me to blog for them. This is a great opportunity for my work to reach a much larger audience! So I will be posting to the V&A blog 1st and then a little later I will post here. If you wish to keep up to date then check out my newest post over on the V&A Blog :)

Let me begin with a little confession – while we like to think of ourselves as immune to them, sometimes we make silly mistakes.

This happened most recently when we began the XRF analysis of some Julia Margaret Cameron photographs to see if the images had been tinted with other elements like gold. Many of you will know that before Instagram and selfies photographs were made with silver salts on paper. So when one is looking for the elements present within a photograph we expect to find silver.

The Darwin image under the XRF machine head. (c) Victoria and Albert Museum, London.

The Darwin image under the XRF machine head. (c) Victoria and Albert Museum, London.

Julia Margaret Cameron took a fantastic photo of Charles Darwin, so we started the analysis with that image only to find the ‘photograph’ contained zero silver. Cue panic from the conservation science team! The analysis was run a second, then a third time (what was the quote about doing the same thing over and over expecting a different result…). We then switched to an image we knew contained silver to see if it was there was something up with the XRF machine – nope, we could clearly see silver on that image. Cue even more panic from the team as thoughts of having to tell people our beloved Darwin image wasn’t what it was supposed to be…

Remember when your teacher would tell you to always read all of the exam question before beginning, turns out you should do that with object lists too… Our Darwin image isn’t a photograph based on silver salts. It is a carbon print and we never spotted this in the internal object description or the object description on ‘Search the Collections’ when we began the analysis. If we had we would never have picked that image to analyse because carbon is too light an element for our XRF to pick up.

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The ‘Search the Collections’ listing for the Darwin image we were working on – See that it clearly states that the image is a carbon print – If i could put a face-palm emoticon here I would…

So what are you doing with a science degree in a design museum…

*NOTE – So the lovely people in the media department at the V&A have asked me to blog for them. This is a great opportunity for my work to reach a much larger audience! So I will be posting to the V&A blog 1st and then a little later I will post here. If you wish to keep up to date then check out my newest post over on the V&A Blog :)

At the very beginning of my internship I posted (in rather mushy way) about the FTIR machine that we have here in the lab. We have quite a good setup here and over the past number of months I’ve been trying to take every advantage I can to use it.

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A close up on the microscope with the sampling cell (silver disk) in position. Using a microscope we can pick out areas in a sample to take out measurement from. (c) Victoria and Albert Museum, London.

FTIR stands for Fourier Transform Infrared Spectroscopy; but what that really means is that it uses an Infrared energy beam to excite the molecules in a material. These molecules absorb part of the energy and with some fancy maths (god bless computers!) we end up with a spectrum from which we can tell a hell of a lot about the material. In a similar way to how bridges resonate at certain wind speeds or a singer breaking a wine glass, the atoms in the molecules vibrate at defined wavelengths. This means that on our spectrum each peak is associated with a certain type of bond.

So what has all this got to do with the conservation science dept. at the V&A! Well we come across a lot of waxes, resins, varnishes, and of course plastics (which is what my internship is about) in the collection. The identification of these materials is important because it not only helps us in carrying out conservation treatments, but also in building up general knowledge and information about the lives of our objects – like on the trade routes used in their manufacture. We can also learn a lot about the decay of objects by looking at peak ratios or the formation of new peaks.

We use two main methods here in the lab which I like to think of as the “quick and dirty” or the “long, but fun” methods. The “quick and dirty” method is technically known as Attenuated Total Reflection (ATR) and works by the phenomenon of total internal reflection. I call it quick and dirty because the sample prep time is quite short – you only need to place the sample on top of a sampling cell that is about 2mm2. It’s dirty because the quality of spectrum is very dependent on external factors like having a uniform thickness, having the correct pressure over the cell, having a uniform sample and most importantly having enough sample to cover the entire cell.

The “long, but fun” method is called transmission as the light source goes through the sample. This method can lead to a spectrum that is clearer and stronger than ATR but is long because of the sample preparation. First one must mount a sample onto a diamond cell.

A little size comparison - the total size of the diamond sampling cell is just smaller that a 5p piece, however we only place the sample in the small clear square. We really only need a tiny sample to make our measurements. (c) Victoria and Albert Museum, London.

A little size comparison – the total size of the diamond sampling cell is just smaller that a 5p piece, however we only place the sample in the small clear square. We really only need a tiny sample to make our measurements. (c) Victoria and Albert Museum, London.

Unlike the ATR method, transmission only needs a tiny sample (size region: grain of fine sand). The small size requirement is due to the ability to use a microscope to focus on an exact spot to analyse. The down side to using a microscope in this way is that you need to align everything correctly which takes time! The fun side is this method requires the detector to be cooled via liquid nitrogen…see my previous post for the fun we have!

An example of the differences between the two methods is perfectly demonstrated by an object we analysed that was treated by Camille Devilliers, an intern in the sculpture conservation department. Camille had a terracotta that had split in half and had been previously repaired by ‘cementing’ two iron dowels into the back of the object. Camille needed to know what the material holding the dowels in place, and what were the other materials used in the previous treatment.  With these pieces of information she could select the correct method to remove the dowels without damaging the object.

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The back of the terracotta that Camille was working on – you would be able to see two iron dowels if they weren’t covered by the brownish beeswax in the center of the object. (c) Victoria and Albert Museum, London.

The graph below shows two spectrum of the same sample from Camilles terracotta – one taken using the ‘short and dirty’ method (shown in red), the second spectrum, in blue, results from the ‘long, but fun’ method. Looking at the graph it’s easy to see that the strength of the red line is much less than the blue; what’s not so easy to spot is that the peaks don’t exactly match – the red peaks are shifted slightly compared to the blue peaks. When we come to search against the database we see that the red line has an 89.23 match with Beeswax AND with Carnauba wax. This isn’t what we like to get when we search! Thankfully if we used the ‘long, but fun’ method we see that the blue line had a 98.25 match with Beeswax and the first 5 results were all forms of Beeswax; no Carnauba to be found which is perfect!

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Spectrum comparison – You might need to click on this image to get a better view of it :) (c) Victoria and Albert Museum, London.

This clarity is whole ball game! When we look at more complex spectra or something that is a mixture, the greater the strength of the sample and the non-shifting peaks means it can be far easier to identify the material.

Mini Post No. 7 – Using a Raspberry Pi to watch a handbag decay

*NOTE – So the lovely people in the media department at the V&A have asked me to blog for them. This is a great opportunity for my work to reach a much larger audience! So I will be posting to the V&A blog 1st and then a little later I will post here. If you wish to keep up to date then check out my newest post over on the V&A Blog :)

So a while back I posted an image of one of the plastic handbags we have here in the Conservation Science Dept. We use these non-museum objects as sacrificial lambs in the aid of heritage science. We have a second handbag that has started to dramatically decay. As we will use any excuse here in the lab to play with new toys “science equipment” we got out a Raspberry Pi. The new camera module for the pi along with a little computer code to set up a time-lapse  is a perfect way to track the rate of decay. We are hoping to let this run for about six months, so come back at Christmas time to see (hopefully) a great video of decaying plastics!

The current setup for a long duration time lapse. Its hoped that we might gain some insight into the decay rate by recording the progress over the next 6 months or so.

The current setup of the Raspberry pi for a long duration time lapse. It’s hoped that we might gain some insight into the decay rate by recording the progress over the next 6 months or so – if nothing else we hope to get a nice film.