Open due to restoration

Open due to restoration

Archaeological finds are important because of what they teach us about the past. They help us to better understand how people in the past lived, what they ate, and what they did. Finds are, literally, tangible evidence of our past.

Finding these objects is important, but so is preserving them. Objects of pottery, metal, glass, bone, wood or leather coming out of the soil are often damaged or incomplete. Their restoration and conservation are therefore crucial. Without treatment, important historical artefacts will be lost.

Restoration often involves highly specialized skills and lots of patience. Every material needs a specific treatment. For example, corrosion needs to be removed from metal objects, soft prehistoric shards have to harden before they can be glued together, and waterlogged wood is sometimes freeze-dried.

After professional treatment archaeological finds are ready for storage, research, exhibitions, and educational purposes.

Archeologie Den Haag stores its archaeological finds at the depot in the basement of the Town Hall and in part also at the De Tempel building. The depot houses an impressive 6,000 boxes of finds.

After over thirty years, Archeologie Den Haag and its conservator Johan van der Helm will be parting ways. It was Johan who founded and expanded Archeologie Den Haag’ conservation department. All the objects you see here have passed through his hands. Thanks to Johan’s efforts, The Hague’s residents can enjoy their city’s top finds for many years to come.

Wood

Wooden objects rarely survive in the soil. Examples are spoons, plates, clogs, or a cartwheel.

Wood only survives reasonably intact in wet conditions, below groundwater level. The lack of oxygen in wet soils prevents micro-organisms like bacteria and fungi from attacking the wood.

Wood needs to be taken from the soil with great care to prevent further damage or loss of information. Wooden objects also need to be stored in wet conditions until conservation treatment can start.

First, wooden finds are carefully cleaned with water to remove dirt.

If left to dry on its own, a wooden object tends to shrink and fall to pieces because its cells no longer contain cellulose.

To prevent that and to preserve the wood, the objects are soaked in a liquid of heated polyethylene glycol (PEG), which replaces the water in the wood cells and strengthens them. Once the PEG has permeated every cell and has hardened, the object is sufficiently stable to be stored and put on display.

Another method to conserve wood is freeze-drying. In freeze-drying, all moisture is removed by exposing the wood to extremely low temperatures under vacuum. This allows the water to evaporate but does not dry out the wood, which would warp its cell structure

PEG treatments and freeze-drying are outsourced to companies which possess the necessary equipment.

Glass

The conservation and restoration of glass objects are delicate processes requiring meticulous and highly precise work.

Dirty glass shards are carefully cleansed with water. Heavily corroded, flaking glass needs special care, for the corrosion layer may be hiding underlying images or engravings.

After cleaning, the shards are sorted by their shape, size, colour and other unique characteristics. This helps to determine how the fragments fit together so that the object can be reconstructed. The glass fragments are glued together with glues developed especially for this purpose, such as epoxy resins.

First, the shards are carefully placed in their correct position with tape. Next, the corners of each fracture are lightly coated with cyanoacrylate, a glue which hardens in seconds. After that, the tape is carefully removed and the remaining fracture lines are slowly filled in with a heated glue, using a syringe.

If the glass is particularly fragile it may need to be consolidated and hardened by impregnating it with for instance paraloid.

Incomplete glass objects can be given transparent synthetic supports to allow them to be put on display safely.

Leather

Archaeological finds made of leather, like shoes, belts or book covers, are often in a very poor condition. Lying in the wet soil below the groundwater table is what made such objects survive.

Leather may dry out, become discoloured and even fall to pieces, making it difficult to restore these finds to their original state.

If leather objects are simply left to dry they will shrink and disintegrate. Several methods have been developed to conserve leather finds, among them the application of polyethylene glycol (PEG), and freeze-drying.

After rinsing in water a wet leather object is placed in a PEG solution. There it stays for a few weeks while the PEG is slowly replacing the water in the leather. PEG conserves leather by stabilizing it and making it retain moisture better so that the object becomes flexible again and breaks less easily.

Freeze-drying is another method to conserve leather. During freeze-drying, moisture is removed from wet leather by exposing it to extremely low temperatures under vacuum. This causes the moisture to evaporate without drying out the leather or warping its cell structure.

The stitching of most excavated shoes has decayed. If it has, the conservator will use new thread to sew the separate parts together, or fixate them on a foam mould. Missing pieces are replaced by new leather patches.

After conservation, leather must be regularly inspected and if necessary treated again.

Bone, horn and ivory

Archaeological finds of bone, horn or ivory can be skeletons, but also objects like a comb, a knife handle, a needle case, gaming pieces, or a prehistoric bone needle.

Before conservation begins, the bone, horn or ivory finds need to be thoroughly cleaned by gently removing any dirt and mud from the surface, using soft brushes and water.

Spending centuries in the soil tends to leave bone objects fragile, soft or brittle. Many need to be consolidated. This is done by applying impregnating agents like an organic glue (gelatine) or a synthetic resin which permeates and strengthens the material.

Metal

Conserving archaeological metals is a complicated process. Each type of metal requires a different treatment. Many finds are covered in a thick corrosion layer, making it impossible to see what the object is.

Particularly iron objects can be badly corroded. Corrosion layers can be removed by a series of mechanical actions, such as brushing, polishing, scouring, or blasting with glass particles inside a special container. Another option is chemical cleaning by means of acids or solvents.

First, superficial dirt and loose corrosion are removed. This can be done manually, using soft brushes and scrapers.

If salt incrustations are present in the metal these are also removed. This is done by bathing the metal objects in an alkaline solution and in demineralized water.

Once the corrosion is removed the object needs to be consolidated to prevent further corrosion. It therefore receives a protective coating with a preservative, for instance an acid-free wax or paraloid (synthetic resin). Some metal objects need to be impregnated, glued and reinforced with an epoxy resin.

Metal finds are then stored in a climate-controlled environment, allowing the conserving agents to keep doing their jobs.

Pottery

Restoring, reassembling and filling in pottery objects is a painstaking process.

Pottery usually comes out of the soil in pieces. Complete pottery objects often come from graves or had been buried in the past as foundation offerings.

Pottery is cleaned with water and soft brushes. However, water cannot be used to clean very soft pottery, like most prehistoric wares. Often such soft pottery first has to be impregnated with a hardening agent like a synthetic resin.

After cleaning the shards are carefully sorted and studied to see if they match with other fragments. A precision job that requires patience.

Matching shards are glued together with special glues which if necessary can be removed again without damaging the object (in other words, they are reversible). The glue is applied to the fractures and the individual shards are carefully pressed together. Tape is used to keep the shards in place until the glue has dried.

Even with all the shards glued together, parts of the objects may still be missing. These gaps are filled in with plaster of Paris or a synthetic resin. With the help of supports or a sand filling the plaster is applied and then sanded or polished to give it a smooth finish. Finally, it is given the same colour and decoration as the rest of the object.

In archaeological restorations, additions should always be kept visually distinct from the original.

Fire bucket, 16th century, Bierstraat 1992

Fragments of a decayed leather fire bucket

On the bucket is a house token in red paint.

The fire bucket was cleaned with water and then conserved by freeze-drying.

Freeze-drying removes moisture from wet leather by exposing it to extremely low temperatures under vacuum. This causes the moisture to evaporate without drying out the leather or warping its cell structure.

Once freeze-dried, the separate fragments were glued onto a base of new leather, using an organic animal glue. A reconstruction of the fire bucket was made.

Drinking glasses, 17th century, Spui 2012

When they came out of the ground these bottles were heavily corroded, showing the flaking iridescent surface typical of corroding glass.

After cleaning, engravings became visible beneath the flakes. Both glasses carry the text: “Vive la Branche d’Orange” and on the other side an orange tree, symbol of the House of Orange. On the stems of both glasses are two tiny portraits.  The glasses were consolidated and reinforced by impregnating them with a synthetic resin.

Cartwheel, 17th century, Binckhorstlaan 2017

Wooden cartwheel, found in 2017 at Binckhorstlaan near De Binckhorst Castle.

The wheel had been reused as the foundation for a well belonging to a 17th-century farmhouse. No nails were used in the wheel’s construction, only wooden pegs . Each component was made from a different kind of wood: the spokes were oak, the hub was made of elm, and beech was chosen for the rim.

The PEG method (PEG = polyethylene glycol) was chosen to conserve the wheel In the PEG method, the moisture in the cells is slowly replaced by a heated PEG solution. The wheel’s separate components were reassembled with glue and cracks and gaps were filled in with wood filler in a matching colour.

Houten wiel

Soil profile, Wijndaelersplantsoen 2007.

This profile shows a series of dark layers. These layers date from the Bronze Age and Iron Age; around 2,000 or 3,000 years ago, they were the ground surfaces on which people were living.

Archaeologists digging in the The Hague soil sometimes come across beautifully coloured layers. Huge vertical slices through the sand, showing layers formed over time, stained and turned over by human activity, then covered again by wind-blown sand.

Important profiles can be preserved by applying a special varnish. For that, a viscous varnish is poured along the carefully smoothed profile from the top. After one day the sand has absorbed the varnish, which is now solid and rubbery. Next, the profile is carefully taken off and placed on a timber board coated in the same varnish. Once the profile is completely dry any loose sand is brushed off and the profile receives a final coating of strongly diluted varnish.

Stitching shoes

The stitching of most excavated shoes has decayed. In that case the conservator will use new thread to sew the separate parts together, or fixate them on a foam mould. Missing pieces are replaced by new leather patches.

Hobnailed sole, Roman period, 2nd century AD, Kijkduinpark 1993

Only the iron hobnails of this shoe survived in the dune sand. The leather has disappeared.

To keep the hobnailed sole intact, it was covered on site with a special varnish. After the varnish had hardened the hobnails could be lifted without disturbing the pattern they were in.

The corroded iron hobnails were impregnated with a synthetic resin.

Grave of a warrior, 7th century, Solleveld 2004

At Solleveld, in the water extraction zone near Kijkduin, Archeologie Den Haag discovered the grave of a warrior. Of the contents of the grave the dune sand had preserved only the metal objects. The body, wood, and all other materials had decayed, visible only as faint traces in the sand.

The thick corrosion layers made it hard to tell what these metal objects were. However, a sword and a spearhead were easy to recognize.

All objects were carefully excavated and brought to the workshop for further study and treatment. X-rays revealed the grip of a shield and a dagger hidden beneath the corrosion.

The hard corrosion layers were mechanically removed. Sadly, very little iron was left inside the objects. Most of it had been corroded. To consolidate and conserve these fragile finds they were impregnated with a special epoxy resin.

The objects from the grave turned out to be a sword, a spearhead , a dagger and a shield grip, and a bronze brooch.

Milestones, Roman period, Wateringse Veld 1997

This milestone shows the ruling Emperor Decius and the distance (IIII MP means ‘4 miles’) to the nearest town, Forum Hadriani. Date 250 AD.

This is an exact copy (a replica) of one of four Roman milestones found in 1997 at Wateringse Veld, along Oosteinde.

The three other milestones:
Antoninus Pius, 151 AD; Caracalla, 212 AD; Gordianus III, between 242 and 244 AD

At first these objects were thought to be stone fragments , but when excavated further they turned out to be milestones. Two thousand years ago, they lined a Roman road.

Procedures were developed to remove each individual milestone from the clay in its entirety and to transport it to the workshop for further treatment. Each milestone was surrounded by a custom-made metal container. It had two sections which were slowly pushed together by means of guide rods and bolts, cutting the milestones loose from their clay matrix. Finally, the containers were filled with sand and transported to the workshop.

There, the milestones were carefully cleaned with water. This revealed the inscriptions chiselled into the stone. Some stone fragments had to be taken apart to remove the clay in the fractures. After months of cleaning and drying the separate fragments were glued together and the porous stone was impregnated with a special synthetic resin. Missing pieces were filled in with two-component mortar in a matching colour.

The original milestones are on display at the Museon Omniversum. Some concrete replicas were made as well; those now stand along Oosteinde.

Silver hoard, Roman period, Rotterdamsebaan 2014

This Roman silver hoard was found inside a pottery beaker. The hoard consists of 107 silver coins, 6 silver bracelets, one large silver brooch , and the remains of a string of beads.

When the beaker was excavated it was not clear what was in it. Back in the workshop the contents of the broken pot were carefully removed. The objects were already suspected to be silver, because of their jet-black corrosion.

The silver objects were freed by wrapping them in aluminium foil and soaking them in a solution of demineralized water and sodium carbonate. This causes a chemical reaction (electrolysis) between the aluminium and the silver corrosion.

The corrosion becomes soft and disintegrates, revealing the coins and bracelets. These were thoroughly rinsed and then carefully brushed with soft brushes. Finally the objects were treated with an acid-free wax to preserve them for the future.

Well, Roman period, Ockenburgh 1993

Part of a well shaft  made of juniper branches, discovered during the Ockenburgh excavations (Kijkduinpark).

To preserve this well, it was first carefully dug free of the dune sand. A supporting layer of wire netting and PUR foam was applied to the outer face of the wattle. In a damp environment, PUR hardens within a few hours. Once reinforced the wattle well shaft could be gently lifted from the trench. Back at the workshop, the branches that made up the shaft were slowly dried and impregnated with a synthetic resin.