STATE OF CONSERVATION

Squares of Chocolate
Forming piles on a wooden surface, the chocolate squares are in an advanced state of deterioration:

• It is infested by micro-organisms, which have perforated the chocolate in several places
• Surface whitening.
• Fragile cohesion, showing signs of cracks and powdering in several places.
• It gives off an unpleasant smell.
• Some squares have shifted. The glue that stuck them together has lost its adhesive power in several places.

Strips of Typed Paper

Sample reference number: 1477

Sample description:
The sample is a piece of chocolate that has become severely altered by the environmental conditions it has been kept in. The study of the sample should allow us to establish the state of alteration and the probable variations in texture.

Analysis:
The sample was observed under a scanning electron microscope (SEM), with which a detailed study of the state of the sample was done. The findings show that this sample has severe surface alterations. The texture of the sample varies depending on the section. The innermost areas of the chocolate sample are less disintegrated and there is less porosity.

SEM image of the surface of the chocolate sample;
this image shows that there are severe surface alterations
and that almost all surface cohesion has gone

Detail of the section of the chocolate sample,
showing that cohesion increases in the innermost areas of the sample

COMPOSITION OF "LINDT" MILK CHOCOLATE

According to the information supplied by Lindt & Sprungli España S.A, today's composition of its milk chocolate is:

1. sugar
2. cocoa butter
3. powdered full-fat milk
4. cocoa paste
5. powdered milk whey
6. powdered skimmed milk
7. malt extract
8. emulsifier: soya lecithin and flavourings
9. cocoa content: 30%

It may also contain traces of almonds, hazelnuts or peanuts, since the same production line is used for several types of chocolate.

TYPES OF CHOCOLATE DETERIORATION
Chocolate loses its flavour approximately one year after its date of manufacture, when many organic molecules forming part of it disappear into the air though a process of oxidation. On a molecular scale, there is a major increase in migrations. In other words, volatile molecules and fats migrate outwards, and flavours and smells migrate inwards.

- Cocoa Butter Blooming
This is caused by exposing the chocolate to warm temperatures that allow the least stable fractions of the cocoa butter or other fats to migrate to the surface of the chocolate. That means that the internal structure of the chocolate has become weak. The fat that initially bound the solid particles together is lost. What once made the chocolate malleable, flexible and elastic is no longer where it should be. The material therefore becomes fragile and powdery. Milk chocolate is less susceptible to blooming.

- Sugar Blooming
This is caused by exposing chocolate to high humidity levels that draws the sugar outwards and deposits it on the surface. Granulated white deposits on the surface are proof of that action.

- Added Products
The weak point that is likely to be attacked by insects or a mould infestation includes added products. When the butter blooms, the oils of the added products (nuts, biscuits etc.) tend to migrate outwards through the chocolate layer. Nuts are the worst for this.
Areas where humidity is high can shrink and cause sugar to bloom. On the other hand, hard areas that impede movements of contraction and dilation caused by temperature changes in the chocolate make it crack.
Areas that have become harbours for bacteria can explode through the force of fermentation products. Over time, as the chocolate becomes brittle, it cracks.
Areas where there is alcohol are subject to alcohol leakage through the chocolate and the migration of saccharose to the surface.

- Humidity and Temperature
One of the main factors involved in the conservation of chocolate is temperature. If it is properly controlled, it prevents the formation of agents that cause it to deteriorate.
Generally speaking, chocolate manufacturers recommend a temperature between 14°C and 18°C. A temperature of 15°C is considered to be the best. One of the golden rules in preventive conservation is to avoid abrupt temperature and relative humidity changes. That prevents crystalline change of the cocoa butter. Blooming occurs rapidly between 25°C and 30°C. Between 22°C and 25°C, chocolate becomes soft, is easily damaged and particles stick to the surface. It becomes distorted above 25°C and starts to melt above 32°C. The melting point depends on the composition of the chocolate, though in general terms we could say that the greater the milk-fat content, the lower the melting point.
As far as relative humidity is concerned, condensation on the surface dissolves the sugar. When the water evaporates, sugar blooms as described above, forming a whitish layer corresponding to sugar crystals. Relative humidity should not exceed 65%.

- Biodeterioration
Mould and yeast can develop when chocolate is exposed to relative humidity above 70%. It does not form a substrate suitable for bacteria. Even when there is condensation, the sugar that migrates to the surface is too highly concentrated to allow them to develop.
Larvae and beetles easily infested the chocolate. In the case in hand, the chocolate was totally infested by beetles.
There are several pest control systems that can be used. They include fumigation, the creation of an inert gas atmosphere (nitrogen, argon, etc.) or an atmosphere with a low oxygen content, and freezing, while taking the necessary precautions when handling the work and preventing the formation of condensation. However, after consulting the company that carries out conservation in the MACBA building - Gestiorquímic - about biological activity, we decided to opt for another type of treatment. That treatment involves placing pheromones - sex hormones - inside the display cabinet in which the work is exhibited, thereby isolating it as much as possible from the outside. Those hormones, which are placed in areas that are out of view, attract the insect by their smell. They form a trap that usually contains a nervous-system inhibitor that paralyses the insect. Thus, the population of insects gradually decreases and so does their growth. It is a long-term treatment that has the advantage of not being harmful to humans. It goes without saying that temperature control is also taken into account. The temperature is kept between 18°C and 20°C and relative humidity is kept between 55% and 60% in the exhibition rooms. Unfortunately it is not possible to keep it at the recommended temperature of 15°C because the minimum temperature in exhibition rooms must be comfortable for visitors.

CONCLUSIONS
When it comes to dealing with the conservation of the work by Dieter Roth, we must be very aware of the fact that, as far as the artist is concerned, deterioration in the work is something that forms part of it. Therefore, if we wanted to be very strict, we should not treat it at all.
However, we should bear in mind that many of his works now form part of public collections and share spaces with other pieces that could become infested. In order to prevent such infestation, we decided to act on the insects and attempt to create a climatic environment that would help conserve it. That includes controlling biological activity, temperature - including any type of light that constitutes a source of heat - and relative humidity. We also decided to isolate the piece inside a display cabinet to prevent a build-up of dust and further infestation by insects attracted by the smell of chocolate. The changes in both the colour of the chocolate and the typed paper form part of the work. In any case, we should bear in mind that it has not been and will not be exposed to a high quantity of light in the Museum. Attempts are made to ensure that it stays at around 80 lux. As a result, no colour changes should occur.