Egg Storage: Epoxy Putty Cases and Bespoke Boxes

Author(s)

Arianna Lea Bernucci
The Natural History Museum
Cromwell Road
London UK  SW7 5BD
+44 (0) 207 942 5116
a.bernucci@nhm.ac.uk

Illustrator / Photo Credits:
©Trustees of the Natural History Museum, London

Description 

Each egg has been housed in an acid-free box with a fold-down front flap and Melinex (polyester) window and an interior tray.  The egg is supported within the tray in an epoxy resin mount lined with Plastazote foam (nitrogen expanded polyethylene foam).   The mount has been fabricated with a flat base to prevent rolling and this has been inserted into a foam cut-out to prevent movement.

Figure 1. Bespoke box with fold-down front and removable tray.

Three-dimensional scanning and printing

Each of the eggs was surface scanned using a handheld structured light scanner (Creaform Go!Scan 20) by Dr. Amy Scott-Murray (3D Imaging Specialist).  These scans were rendered into 3D digital models which were then used to print 3D replicas from Polylactic Acid.  Each egg replica was printed in two halves which were later adhered together to make the mounts.

Figure 2. Two halves of a 3D printed Great Auk Egg replica used for fabricating the mount.

Materials, Tools & Supplies

Mount

1. Epopast 400 paste (epoxy resin with fiberglass filler)
2. Epopast 400 hardener (epoxy resin)
3. Plastic tub (for mixing Epopast)
4. Weighing scale
5. Melinex (mylar)
6. Rolling pin
7. Industrial Methylated spirits (IMS)
8. Grinding tool (e.g. NSK, Dremmel, sandpaper)
9. Plastazote foam (2mm thick) (nitrogen expanded polyethylene foam)
10. Scalpel handle
11. Scalpel blades (#11)
12. Pliers
13. Glue gun
14. Low-melt glue

Box materials

1. Acid-free card – fluted (2mm thick)
2. Plastazote foam (2mm & 1cm thick)
3. Stanley knife
4. Stanley knife blades
5. Scalpel handle
6. Scalpel blades (#11)
7. Pliers
8. Ruler, set square
9. Pencil
10. Eraser
11. Cutting mat
12. Crayon
13. Glue gun
14. Low-melt glue
15. Melinex
16. 3M double sided tape
17. Bone folder
18. Awl
19. Nickel-plated rivets
20. Hammer

Construction

Preparation of 3D print   

1. Adhere* 2mm thick Plastazote (nitrogen expanded polyethylene foam) to the curved surface of the 3D print using hot melt glue. (Note: If you apply hot glue and then stretch and flatten the foam against the curved surface while the glue is still hot– it should stretch enough around the shape to not need cutting.)
2. Trim excess Plastazote with scalpel.
3. Wrap entire print with cling film.
4. Place wrapped egg in container filled with sand or crushed garnet.

Figure 3. Replica is ready for application of epoxy resin paste.

Mount Fabrication

1. Mix Epopast 400 paste and resin according to manufacturer’s instructions, while wearing the appropriate Personal Protective Equipment outlined in the SDS/COSHH.

Figure 4. When Epopast is properly mixed it should be an even green colour.

2. Place enough Epopast to cover one half of the egg between two sheets of Melinex and roll to 5mm thick with a rolling pin.
3. Remove Epopast ‘pancake’ from Melinex and place on top of the egg (side with Plastazote). Wrap the Epopast snugly around the egg to about halfway.

Figure 5. Epopast applied to replica, before smoothing.

4. Tip: You can use Industrial Methylated Spirits (IMS) to smooth the surface. Remove excess Epopast and ensure that once hardened it can be easily removed (e.g. do not cover the egg so much that the paste undercuts it – making it impossible to remove.

Figure 6. Epopast has been smoothed with IMS.

5. Add extra paste on the top center of the egg (this will become the ‘foot’ that keeps it from rolling).
6. Once finished shaping and smoothing the paste, cover with cling film.

Figure 7. Epopast is covered with cling film and left to set for 24 hours.

7. Use a rigid, flat surface to press into the ‘foot’ of the paste. This will give it a flat surface so that the mount does not roll.

Figure 8. A ‘foot’ is added to the egg case to provide stability. A rigid material can be used to press this flat to prevent rolling.

10. Allow to set for 24 hours.
11. Remove the cling film. Carefully remove the egg from the Epopast.  It should be rigid and inflexible.  This may require a little bit of wiggling. Tip: Wear leather palmed gloves when doing so as there may be sharp fragments of fiberglass.
12. The Epopast can now be sanded and painted. Use special tools to grind the Epopast – such as a Dremel or NSK.  If not available sandpaper is an option. Tip: Use particulate extraction when carrying out this work.   Please note that PPE outlined in the appropriate SDS/COSHH documents should be worn.

Figure 9. Epopast has been sanded and smoothed using an NSK – it is now ready for foam.

11. The mount is then painted with an acrylic paint.
12. Adhere 2mm thick Plastazote using low-melt glue to the interior surface. Tip: You don’t need to cover the entire case with Plastazote – you can adhere strips that provide enough cushioning to protect the egg.

Figure 10. Epopast has been lined with strips of foam and painted black.

Tray Fabrication

Figure 11. Removable tray with Plastazote lining.

1. Measure the specimen – Measure and note the width and length of the specimen. Add at least 2-3 cm to these measurements to ensure there is a protective border surrounding the specimen.  (Tip: Always err on the side of caution and round the numbers up).
2. Base layer – Cut the 2mm thick Plastazote into a rectangle using your Stanley knife and the width and length dimensions calculated from the step above. This will be the base layer for the specimen to rest on.
3. Stabilizing layers – Do the same as step 2 with a thicker piece of Plastazote (1cm) to create a rectangle of the exact same size. (You may need more than one layer or thicker foam depending on the size and complexity of the specimen).
4. Place the specimen on the thick Plastazote and carefully trace around it using a white pencil or crayon. (BE CAREFUL NOT TO MARK THE SPECIMEN!!!).  Cut the shape out of the foam using the scalpel blade.
5. Measure the length, width and height of the Plastazote rectangle.
6. Use the tray template, ruler and pencil to mark out the measurements on the white side of the acid-free card and cut out using the Stanley knife.

Figure 12. Tray template.

7. Use the bone folder and Stanley knife to crease and cut the appropriate lines that have been marked. (The tray template indicates which lines should be cut and which should be creased.)
8. Fold the tray where creased.
9. Use the awl to poke holes where indicated on the tray template. Tip: do this while having the corners folded together so holes line up.  Use scalpel to cut away excess card that gets pushed out through the holes.
10. Insert rivets through the holes (male rivet inserts into female). Use hammer to pound the rivets together.
11. Place the Plastazote layers inside.

Box Fabrication

Figure 13. Box without lid.

1. Measure the height of the specimen. Add 2-3cm to this to ensure adequate space above the specimen once the lid is placed.
2. Base measurements: Measure the width and length of the tray just fabricated. Add 5mm to each so that the tray will fit snugly in the box, but not too tightly.  Lid measurements: Measure the width and length of the base and add 5mm to each for the lid.  The height of the lid is up to the discretion of the maker as this will depend on the size of the box.  It should be high enough to close the box securely but not so high as to make removal impossible.
3. Use the following steps to make both the lid and base of the box.
4. Use the base or lid template to calculate the measurements. Total the width, length and height to get a maximum size for the piece of card needed.

Figure 14. Box base template.

Figure 15. Box lid template.

5. Mark (with a pencil) the box base or lid pattern using the measurements calculated with the box template.
6. Melinex window – Measure and mark out a rectangle in the center of one of the sides of the box (maker’s discretion as to which). This creates a ‘window’ so the specimen or label is visible through the side.  (Tip: Rectangle size is up to the discretion of the maker – needs to be big enough to see specimen, but small enough that side still provides protection and is strong enough for the lid.)  Cut a piece of Melinex (polyester) to cover the rectangle cut out from the lid at least a 5mm overlapping border around the edges.  Using double-sided sticky tape, adhere the Melinex rectangle to the exterior surface of the lid.  Using a spare piece of card cut out a rectangle the same size as the piece of Melinex.  Cut out its middle so you are left with a 5mm thick rectangle.  Use double-side sticky tape to adhere Melinex to this piece and then sticky tape to adhere both pieces to the exterior of the box lid.
7. Use a bone folder and Stanley knife to crease and cut out the appropriate marked lines (from template). Fold all creased lines.
8. Use an awl to poke holes through the corners where indicated on the template. (Note: The base only receives rivets in two corners, as one side will not attach, but fold down when lid is off).

Figure 16. Box with front flap open.

9. Insert rivets through the holes (male rivet inserts into female). Use hammer to pound the rivets together.

Figure 17. Finished box with lid and Melinex window.

Keywords

Egg, Byne’s Disease, Tray, Box, Mount

Collection Type(s)

Natural Science Specimens; Eggs