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Repairing and Preparing FOSSILS.

     

 

Introduction

 

Many of the best fossil locations are located on the coast, where the rate of erosion is at its highest.  The rate of erosion is most rapid in areas where the rock is relatively softer i.e. chalk, shale and clay. If collecting in these areas the first and most important step in protecting your finds is to prevent them from drying out. This is necessary as allowing them to dry before applying water could splinter fragile fossils.  Once home the next step is to soak the fossil in cold water to remove any trace of sea salt from the rock.  If this step is missed the fossil may simply disintegrate after a couple of years, especially chalk specimens.

 

Soaking chalk fossils in fresh water to remove salt from the rock

 

Ideally the fossils should be soaked for at least two weeks.  The picture above shows a collection of chalk fossils from Eastbourne undergoing this treatment.  If soaked outside cover the container with a dark cover to prevent algae from growing on the fossils.

 

Once the soaking is complete the fossil is ready for cleaning.  This can be completed while the fossil is wet or dry (if you have access to an abrasive tool).

Always keep cleaning and repairing fossils to the absolute minimum.

 

It is often the case that fossils will be completely or partially covered with the surrounding material, known as the 'matrix'.  In some instances the matrix can be easily removed, while at other times the material is much more resilient.

 

There are a number of techniques for preparing fossils, ranging from the simple use of a pocket knife, to the more advanced methods involving organic acids.  In deciding which technique to employ it is important to consider how fragile the fossil is, and how hard the surrounding matrix is.

 

The basic tools necessary for preparing fossils include:

 

    Penknife/Chisel/Dentists probe

    Small brush/Toothbrush

    Paintbrush

    Clear Enamel

    Cloth

    Epoxy glue

    Polyfilla

 

Compressed Air-pen

 

The professional choice for fossil preparation are airpens.  These tools act like miniature pneumatic drills, cutting through unwanted matrix to reveal the fossil.  The pen itself is connected by a long pipe to a motor powered compressor unit, which provides air to the tool.  At the tip of the tool is a tungsten tip that moves back and forth around 40,000 times per minute!

 

Airpens make easy work of tough matrix.

 

Unfortunately the initial outlay for this equipment is quite high, but the results can be excellent.  If you're considering purchasing an Airpen please contact us and we'll direct you to our recommended supplier.

 

 

Sharp implement

 

The easiest and most commonly used technique for cleaning fossils involves the use of a sharp implement, often a penknife or dentist's probe.  Such tools must be used carefully to avoid slipping, which could result in damage to the fossil or yourself.

 

Ammonite from Seatown (Dorset) prepared with a penknife

 

Sharp implements are most suited to soft matrix, such as the Jurassic clay found at Lyme Regis.  The ammonite above (found at Seatown) was prepared using a penknife to carefully cut away the excess material.   In this instance the ammonite was exposed after only half an hour, revealing a high quality specimen.

 

This technique is also well suited to preparing Cretaceous fossils found in chalk, including echinoids commonly found at Seven Sisters in East Sussex.

 

Echinoid in chalk prepared using a penknife

 

Liquid Paraffin

 

During the process of fossilization, the original colour is lost.  However, in some instances, the minerals which replaced the original creature, such as those preserved as pyrite, may themselves contain a variety of colours.  Applying a coating of liquid paraffin can be used to highlight these colours.

 

Using liquid paraffin to highlight colour depth

 

Liquid paraffin, which is otherwise used as a laxative, is available in most chemists.

 

Enamel/lacquer/PVA

 

To enhance the appearance of fossils we recommend the use of PVA Glue (1 part glue to 4 parts water).   Applied thinly the glue leaves a clear and slightly shiny surface, which often gives greats results. You can also use enamels (not usually recommended), however too much or applied in the wrong way can ruin a good specimen.  However enamels can act as effective protection for pyrite, which would otherwise react to the moisture in the air.

 

 

Applied thinly a layer of PVA (recommended) or enamel can enhance and protect fossils.

 

The end result should avoid a gloss appearance.  For this reason it is unsuitable to apply the enamel using a conventional brush.  Instead apply a small amount of enamel to a piece of cloth, and apply it thinly to the fossil's surface.

 

When treating pyrite, it is first important to soak the fossil in tap water to remove any salt from the fossil.  Applying a layer of enamel to the pyrite will shield it from the air.  This is important, because left untreated, pyrite can quickly decay.

 

Setting in Polyfilla

 

For some fossils it may be advantageous to surround the fossil with a stronger material such as Polyfilla.

 

 

Polyfilla can provide a strong surrounding for particularly fragile fossils

 

The example above is a trilobite from Shadwell quarry in Much Wenlock (Shropshire).  The matrix surrounding the trilobite is extremely fragile and would have crumbled away without immediate treatment.  To begin with, mix a small quantity of Polyfilla in a flat dish, then press the fossil into the mix.  After about 15 minutes, take a sharp knife and cut around the fossil, as pictured above.

 

Leave the Polyfilla to dry for a further 24 hours before handling.

 

Repairing - Epoxy Glues

 

It's inevitable that some fossils will become damaged during transit, or cleaning.  All is not lost though, with the right glue it's usually possible to make repairs to the fossil.  Epoxy glues are a popular choice, as they bond within several minutes, but allow several minutes to make adjustments if required.  However the downside of using theses glues is the inability to reverse the repairs if necessary.  If the fossil is of particular value, it is worth considering the use of 'Paraloid B72', now used in most museums. It’s a methacrylate co-polymer and although it is very strong it can be dissolved with acetone.  (To order Paraloid B72 call 01865 747755).

 

Epoxy glues, such as Araldite, include a 'Resin' and a 'Hardener', which when combined create a long lasting and strong bond.

 

Epoxy glues provide a strong and long lasting bond

 

To begin repairs to the fossil, prepare a small quantity of Epoxy glue as specified in the instructions accompanying the product.  Then place a very small amount on one side of the broken piece.  Bring the two sides together and press them firmly in place.  The glue will immediately provide sufficient bonding to hold them together.  Allow up to 24 hours for the repair to bond completely.

 

     

Repairing a fragile ammonite from Seatown (Dorset) with Epoxy glue

 

Many thanks to Nigel Larkin for his recommendations .

 

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