Tag Archives: conservation

17th Century Modern Materials

*Head over here to see the latest blog post 

IMG_5663

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…

2006AF5121

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.

Capture

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.

1

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.

2

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. 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.

Darwin

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.

photo 2

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.

Image of back small

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!

FTIR WAX

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.

 

Mini Post No. 6

So I have been researching about Polyvinyl chloride (PVC) over the past while and I came across this lovely example in the lab of the major danger associated with PVC. Many of us have our family photos kept in ‘plastic’ photo albums – most of these are going to be made from PVC. The biggest danger to our valuable family photos isn’t fire or theft, its the album itself! The plasticizer is very prone to migrating to the surface of PVC, if it’s not removed it forms what’s known as sweat beads. These beads destroy photos! Take a look at the two images below to see just what kind of damage can be caused!

Later in the month I’ll do up a more detailed blog post about PVC. Till then, if you want more information about how to protect your photographs have a look what the British Library and The National Archives have on the topic.

A photograph has been totally distroied by the migraetion of plastizer from the album sheets. (c) Victoria and Albert Museum, London.

The photograph has been totally destroyed by the migration of plastizer from the album sheets. (c) Victoria and Albert Museum, London.

Close up on the face of a person in the photograph. The image had lost almost all definition. (c) Victoria and Albert Museum, London.

Close up on the face of a person in the photograph. The image had lost almost all definition. (c) Victoria and Albert Museum, London.

 

Kaleidoscope House – A dolls house for the ‘child’ interested in modernist architecture

One of the nicer elements of my job is the exposure to the wonderfully diverse collection that we have here at the V&A. Later in the year the Museum of Childhood is putting together a wonderful exhibition on Dolls houses. We (my supervisor and I) were asked to consult on one of the more unusual dolls houses that will make up the exhibition – Kaleidoscope House

Kaleidoscope house - a mini modernist masterpiece (say that 10 times fast!)

Kaleidoscope house – a mini modernist masterpiece (say that 10 times fast!)

The example of Kaleidoscope House that we have here at the Museum of Childhood does not have its artwork attached to the walls. As they were purchased separately the museum could not, in good faith (ethics and all that!), adhere the artwork to the plastic walls without investigating how the artwork, adhesive and plastic would react over time. I was set the challenge to devise a simple and quick experiment to do this.

When we talk about the lifetime of a collection or an object we need to look timelines beyond our own lifetimes or careers. Research into this topic indicates that people would like an object to survive in a “usable” form for 100-500 yrs. Clearly we can’t wait around to see how objects react to their environments, nor can we always look to the past as we may not know the exact conditions of storage. This is where artificial aging comes into play. We know that exposure to light, especially UV light, is very damaging to plastics (and to objects in general. I can’t believe I just linked to the Daily mail…). We also know roughly the amount of light an object will receive when on display:  50 lux for 10 hours a day for 365 days = ~180Klux per year. By placing objects in a light box, exposing them to very high light levels we can mimic the the effect of years of light exposure in a short period of time. There are other factors which are important, temperature and relative humidity being the other two major effects. I wont go into more detail and risk boring you all but Robert Feller has a very good book on the topic of Accelerated aging which you can find for free here and it’s well worth a read, even if it’s just to brush up on the basics of what tends to age things!

Anywhos… back to my plastic dolls house. Through a bit of research – basically procrastinating while reading the wonderfully in-depth world of mini modernist houses over at http://modernminihouses.blogspot.co.uk/ we confirmed our theory that the walls were made of polystyrene, a common plastic used for this type of application. The experiment was a simple idea – get materials similar to those intended to be used, test a range of different adhesives and expose everything to 5 years’ worth of light! CD Jewel cases are also made of polystyrene allowing us to use cd cases that we had here in the lab – to better match the current conditions of KH we used cases that were of similar age. The amazing people over in the paper conservation department gave me some mount board of a similar thickness to the artwork; they also provided three common adhesives used in paper conservation – wheat paste, EVA and Methyl cellulose. The other interesting adhesives we tested were blue tack (yup, regular blue tack!), Paraloid b72 (a very common adhesive used in conservation) and Sugru (a new silicon based adhesive a bit like blue tack, only yellow and much stronger/permanent. It is also very popular in the hacking community atm.)

CD case ready to be tested - note that I used an excess of adhesive to see the 'worst case scenario' when trying to remove the 'artwork'. In real life you would try to use much less adhesive than this. (c) Victoria and Albert Museum, London.

CD case ready to be tested – note that I used an excess of adhesive to see the ‘worst case scenario’ when trying to remove the ‘artwork’. In real life you would try to use much less adhesive than this. (c) Victoria and Albert Museum, London.

CD jewel cases in the light box, propped up so that front and back get similar light exposure. You can see that a few of the adhesives have failed right from the beginning! (c) Victoria and Albert Museum, London.

CD jewel cases in the light box, propped up so that front and back get similar light exposure. You can see that a few of the adhesives have failed right from the beginning! (c) Victoria and Albert Museum, London.

After leaving the test to run for 96 hours (who wants to do the math to work out the average light levels in the light box…) we then tried to remove the mount-board and the adhesives. Before starting the tests I thought that wheat paste would work the best – how wrong was I! It was the 1st to fall off, along with Methyl cellulose – they didn’t even last a day!

Sugru was very difficult to remove, and I really thought I’d crack the plastic – I didn’t, but as you can see below I couldn’t remove the mount-board cleanly. Removing EVA was very similar and the risk of cracking the plastic rules these two adhesives out of contention.

Sugru...I was able to remove this from the plastic CD case, but not the paper artwork - it wouldn't want to be a Constable painting i was trying to take off! (c) Victoria and Albert Museum, London.

Sugru…I was able to remove this from the plastic CD case, but not the paper artwork – it wouldn’t want to be a Constable masterpiece I was trying to remove! (c) Victoria and Albert Museum, London.

Blue tack left a nasty residue behind. Researching into what goes into blue tack we found out that it contains a small amount of Xylene. Have a look at the video below to see what happens (admittedly in a pretty extreme case) when xylene and polystyrene come into contact with one another! Not what you want to have happen and leaving the residue on the surface would increase the risk of localized damage to the object.

You can clearly see the residue left behind on the surface! (c) Victoria and Albert Museum, London.

You can clearly see the residue left behind on the surface! (c) Victoria and Albert Museum, London.

So after all that work we found out that none of the major adhesives were suitable for this project (what was it that Thomas Edison said…) . In fact some of them could have totally ruined our lovely dolls house! The curators were thankful for the information we had given them, but also a little sad as they are now back to square one. We think we might be able to hang some of the artworks using nylon wire (again, a pretty common thing to do). The risks to the object are increased the more times the blue roof has to be taken on and off, but it also means we won’t have access to hang every piece of art. A small price to pay for keeping this lovely object in great condition! You can come see what methods we used when the exhibition opens later in the year.