Embedding Techniques

Transcription

1 Biological Control Info Page Embedding Techniques Used to Preserve Biocontrol Agents and Invasive Plant Material into Crystal Clear Resin 2000 Forest Practices Branch Biocontrol Development Program

2 Table of contents Introduction...3 Recommendations... 3 Prepare Specimens and Identification Labels... 3 Biocontrol agents... 3 Plant materials... 4 Identification labels... 4 Embedding Prepared Specimens in to Crystal Clear Resin... 5 Required materials and safety equipment... 5 Using Crystal Clear Resin... 5 Prepare specimens for embedding... 5 Mixing Crystal Clear with catalyst... 5 Mixing instructions... 6 Test the cast for hardness... 7 Remove the cast... 8 Grinding and polishing... 8 Storage

3 Introduction The purpose of this document is to outline the techniques used to preserve specimens in synthetic resin (bio-plastic) for use as displays and education purposes. The following information offers guidance to individuals who are experienced and familiar with the equipment and materials used for the embedding of specimens, in a safe and secure environment. The Province of British Columbia does not accept responsibility or liability for any costs or damages that occur as a result of the procedure. Recommendations The products used in this procedure are generally available from hobby or scientific equipment outlets. Thoroughly review the products information sheet and safety recommendations before starting, and proceed only if they are fully understood. Contact the manufacturers if there is any uncertainty about using the products. The procedure should be read in its entirety before initiation. It is advised to practice the procedure first with less desired specimens prior to preparing rare specimens. Prepare Specimens and Identification Labels Biocontrol agents Biocontrol agents must be collected and prepared before they become dry. Dehydrated specimens will not withstand any manipulation. For best results prepare the biocontrol agents in their natural position as soon as possible. By positioning their legs, wings, antennae, etc., a life-like specimen can be created. Refer to the collection and drying instructions found in: Borror, Donald J. and Richard E. White Peterson Field Guides insects.; Agriculture Canada The insects and arachnids of Canada part 1. Collecting, preparing, and preserving insects, mites, and spiders; or, Any other source that provides complete specimen preparation guidelines. Once the biocontrol agent specimens have been prepared and dried they can be stored until they are embedded into the resin. Store the specimens in a protective box or container to prevent them from becoming damaged or dusty. 3

4 Plant materials Plant specimens must be thoroughly cleansed and to be free of soil and dust particles. Clip the plants into the appropriate size to fit the resin mold, allowing for some shrinkage. The plants must be completely dry before preparing the molds. This can be achieved using drying silica. Drying procedure: Select a suitable sized container to layer the silica and plant material into. The container should allow space around the plants of approximately 1.5 to 2.5 cm on top, bottom and sides to provide sufficient silica to cover the specimen entirely and allow for complete drying. Pour a layer of silica 2.5 to 5 cm thick in the bottom of the container and place the plant specimen on top. If more than one specimen is to be dried in one container do not let any parts touch. With a small scoop, pour silica around the plant specimen, gently shaking the container so the silica sifts under and completely around all plant parts. Carefully keep pouring and sifting the silica without disturbing the natural shape of the plant. When the specimen is completely covered, add approximately 2.5 to 5 cm of silica on top and then seal the container. Let the specimen dry for approximately 3 to 4 days (larger or multiple specimens take longer to dry). When plant specimens are dry, remove them from beneath the silica. Place plant specimens on top of the silica and close the container again for an additional 2 to 3 days. When dried, carefully shake off all traces of silica. Store the specimens in a protective box or container to prevent them from becoming damaged or dusty. Identification labels Labels can be made from adhesive-backed computer labels and white plastic greenhouse labels (marking stakes approximately 1 mm thick). In most situations the identification labels should be white, but, other colours can be used if desired. Type two copies of the identification information into the computer label template, using appropriate font, size and style, and print. Cut the white plastic greenhouse label and the adhesive-backed label into identical sized pieces. Attach a copy of the adhesive label each to both sides of the cut plastic label. Set aside until the resin preparation begins. 4

5 Embedding Prepared Specimens into Crystal Clear Resin Required materials and safety equipment Mylar paper or wax paper to work on Safety glasses Protective gloves Crystal Clear Resin Catalyst Felt pen Pointed tweezers Non-waxed paper cups Disposable wooden stir sticks Molds (polyurethane or aluminum) Needle-nose hand tool Lamp (snake lamp with 60 w bulb is recommended) # s 180, 400, & 600 Sandpaper Felt Liquid Abrasive Liquid polish Shami Acetone for cleaning Using Crystal Clear Resin When you mix the Crystal Clear Resin with the catalyst the color changes from blue to green. As the heat reaction progresses, the plastic gels and then becomes crystal clear. The preparation area must be virtually dust free to ensure a quality end product. Prepare specimens for embedding Before you create your resin mold, the biocontrol agents, plant specimens and labels should be submerged in a separate container in un-catalyzed resin. This will remove air bubbles from the surface and any air pockets from inside the specimen. Pour approximately 2.5 cm of un-catalyzed resin into a clean, nonwaxed paper cup. Use tweezers to carefully submerge the specimen into the resin. If the specimen floats it will need to be weighed down (a small metal washer will work). Note: The air bubbles rise to the surface as the specimen is saturated. Cover the container with a sheet to keep dust out and leave overnight. Do not rub the ink on the labels, they will smudge. When the labels are taken out of the container with tweezers, the excess resin will run off the ends. Place the label into the mold. Mixing Crystal Clear with Catalyst The resin layering procedure will take several uninterrupted hours to complete. It is critical that sufficient time be allocated to complete the entire process. 5

6 See the Table 1 for the mixing proportions. The percentage of catalyst declines with each layer added which slows down the hardening process and avoids cracking. Table 1. Poly Mold Catalyst Proportions Single Layer Pour Multiple Layer Pour Layer Drops of Catalyst per oz. of resin Layer Drops of Catalyst per oz of resin 1/8 inch ¼ inch ½ inch ¾ inch ½ inch Several procedures were tested. Best results were achieved when using a 3-layered process as shown in Figure 1 below. Figure 1. Recommended layering process Mixing Instructions Layout the working area in a location that can remain undisturbed for the entire process. Place mylar or wax paper on the work area surface. Arrange the selected molds relatively close together so they can be accessed easily during this process. Keep the area free of dust. Table 1 values are average. Smaller amounts of catalyst are better suited for moths while larger amounts are suitable for other biocontrol agents. If some specimens continue to develop problematic air bubbles, even after they have been submerged as previously described, a lower proportion of catalyst may be the answer. The lower rates of catalyst allow more time to remove trapped air bubbles as the resin does not harden as quickly. Use a black felt marker to mark the desired quantities on the outside of nonwaxed paper cups. Pour in appropriate amounts of resin and catalyst needed for the chosen molds. Stir gently with a clean, dry stick, mixing thoroughly and evenly for about a minute. Mix gently to avoid adding excess air and consequently creating air bubbles. If air bubbles develop, let the resin stand for a short time to allow the bubbles to rise to the surface. Very gently, pour the first layer (supporting layer) into the mold as shown in Figure 1, taking care to prevent any air bubbles from developing. Do not pick up 6

7 or move molds once the first layer is poured. Adjust a lamp over the molds and inspect the layer for trapped air bubbles. Working quickly, use the needle-nosed tool to work the trapped bubbles to the surface. Revisit each mold frequently and remove air bubbles as they develop. The resin will begin to gel in 15 minutes. Once the resin starts to gel, do not work with it. It is advised to work in small batches with only a few molds that can easily be tended to during this critical process. Once the layer gels to the point it no longer flows it is ready to support the specimen. This can take 25 minutes to 2 hours from the time the layer is poured. Check the resin consistency by poking the surface gently with the needle nosed tool. Continue to check the molds. Do not allow the resin to harden between the pouring of each layer. When the resin has thickened sufficiently the specimen can be added. Using the needle nosed tweezers, carefully remove the specimen and its corresponding label from the uncatalyzed resin and place it on absorbent towelling to drain off the excess resin (this takes about one minute). Use hand tools to arrange the specimen and label into a desired position on the supporting layer of resin in the mold. Press the specimens down lightly to expel any air that may be trapped beneath them. Without piercing the first resin layer, carefully remove any air bubbles. Let the resin mold sit for minutes to allow the specimen and label to adhere to the supporting layer. Prepare the second layer (retaining layer) of resin mixture according to the chart and follow the same precautions to prevent air bubbles as was done with the first layer. Carefully pour the mixture into the mold as indicated in Figure 1. Once more, position a lamp over the molds and monitor frequently while the second layer sets (approximately 25 minutes). Monitor and quickly remove air bubbles. Again, do not pierce the first layer. When the second layer begins to gel you can prepare the third and final layer (covering layer). Mix the resin and catalyst according to proportions in Table 1 and repeat the pouring and monitoring process used with the first two layers. Remove air bubbles while taking care not pierce the layer below. Once the resin begins to gel, place a lamp 9 to 12 cm (3 to 5 inches) above the molds for 4 to 5 hours. Remove the lamp or turn it off and allow the molds to cool to room temperature. Test the cast for hardness The cast (resin mold) may take several days to cure. During this process, continue to keep the work space dust free. A properly cured cast will have pulled away from the sides and face of the mold. The resin should not be tacky. Test the cast by tapping the hardened surface with a clean stir stick, it should sound like tapping hard plastic. If the cast is still tacky, it should be left for a few more days to finish curing. Do not handle the block until it is completely dry. Minimize handling and do not touch the block with your fingers or any unnecessary tools as blemishes and fingerprints are easily transferred to the surface and very difficult to cover up or remove. 7

8 Remove the cast Once the cast has adequately cured it is ready to be removed from the mold. Invert the mold over a piece of felt and flex the mold as you would an ice-cube tray. If the resin mixture was properly catalyzed, the hardened block will easily drop out. Clean the polyurethane/aluminum mold with acetone. Rinse thoroughly prior to re-use. Grinding and polishing The more effort expended on grinding and polishing, the better the cast will appear, therefore, allow sufficient time for this process. If deep scratches or blemishes occur, they can be removed with the grinding procedure. Once the cast has been removed from the mold, it is necessary to grind its surfaces before it is polished. Wet the back of a sheet of course emery paper (#180 grit) and place it on a smooth surface (wetting the backside makes it stick to the work surface). Add a small amount of water to the grit side of the emery paper to create a puddle and establish what is referred to as wet grinding. Using a forward and backward motion, move all six sides of the block through the puddle and across the emery paper. Wet grinding eliminates dust and also provides an even cut. Rinse the block with water to inspect the grinding process. Once the block has been satisfactorily worked, rinse it in water and go to the next step. Repeat the grinding process, but this time use # 400 grit emery paper. Repeat the grinding process once more using the #600 grit emery paper. Once the block has been satisfactorily worked with the 3 grit levels of emery paper it needs to be further ground with a liquid abrasive. Wrap a small wood block with a piece of clean felt to create a felt block. Apply a small amount of liquid abrasive to the felt block and polish the cast by using back and forth motions. When finished, the cast should be smooth and transparent. Finally, polish the cast. Prepare another felt block using a fresh piece of felt. Do not use the same piece of felt that was used when applying the liquid abrasive, always keep the two separate (label if necessary). Apply a small amount of liquid polish to the felt block and rub all the cast surfaces with a back and forth motion. Storage The resin blocks will scratch easily and should be stored in protective layers of fabric or displayed in a case lined with soft fabric. They will also discolour if stored in hot locations or direct sunlight. Use a shami cloth to remove dust or fingerprints. 8