This is my method of treating fractures with Opticon. I almost always treat the fracture after all of the grinding, sanding and polishing steps are completed. I have found that treating before cabbing usually results in the fracture propagating more during the cabbing and the new fracture area is obscured by the Opticon so it can't be retreated.
I use my bench "gooseneck" lamp with a 100 watt clear bulb to heat the cab and Opticon. It provides more than enough heat to achieve a good healing action.
Here is a photo of the Opticon and hardener. This size container is the most popular and will do many cabs.
I use wells cut from an aluminum muffin pan to do the heating steps. You can shape a little spout on the edge to pour the excess Opticon back into its container.
I place the cab in the well and cover it with Opticon. Make sure that you have cleaned the cab with soap and water. I also place the cab in my ultrasonic cleaner to get all of the polishing compound out of the fracture. I have found that it is almost impossible to remove the polish with hand scrubbing. A few seconds in the ultrasonic is all that is needed. The last step before placing the cab in the well is to clean all the fingerprints off with denatured alcohol.
If the cab is a little large for the well you can easily reshape the well.
Next I place the well under the lamp.
Lower the lamp down as far as you can get it without the bulb making contact with the Opticon. I like to place something under the well as a heat shield to protect the bench top from getting overheated.
The heat will cause the Opticon to give off some odor so if this is objectional you can place a fan nearby. I leave the heat on the Opticon/cab for 3 hours. The cab will get so hot that you cannot touch it with your bare fingers! By getting it this hot the cab will expand and the fracture will be wide enough for the now very hot and fluid Opticon to fully fill the fracture.
After the three hours you can remove the cab with tweezers or pliers and wipe the excess Opticon off with a napkin. Wipe off all that you can get off. Carefully pour nearly all of the hot Opticon back into its container. Leave about 1 teaspoon of resin in the well.i
Pour this excess resin into a paper cup that has been cut down shorter.
Add a few drops of hardener. The instructions call for a 10 to 1 mixture of resin to hardener.
Stir with a wood popsicle stick.
Get a paper plate, cut a few pieces off a plastic ceramic tile spacer and arrange them on the plate. These will allow you to keep the treated cab up off the surface of the plate.
Lay the cab on the spacers and apply a narrow line of resin/hardener over the fracture line. Do the same on the girdle of the cab and on the back.
Place the cab back under the light and lower the lamp to it but not as close as before.
Leave it this way for an hour or so. Turn off the lamp and when the cab is cool enough to touch check that the Opticin has set up real hard.
File off the excess hardened Opticon and admire your success. As you will see, the less excess Opticon that you add over the fracture, the less you will have to file off.
I have tried to place the heated cab in the Opticon in a bell jar under a high vacuum to increase the penetration of the Opticon with very limited success. The vacuum tends to vaporize the Opticon especially within the fracture and draws it back out of the fracture. Maybe placing the cab in a vacuum before any treatment will pull any water that might be in the fracture might help but generally heating the cab slightly before adding the Opticon will do the trick.