The fusion method is the procedure employed to permanently affix the toner to a sheet of paper. It is the most discriminating class characteristic.
Types of Fusion
The following are various types of fusion:
1. Radiant Heat
Intense heat is applied to dry toner during the fusion process which has a glossy, bubble appearance.
Liquid toner is also included in this category because heat is involved in the fixing process. Liquid toner will have a flat appearance, and the paper fibers will appear to be dyed.
Examples: Xerox 1075 and IBM Copier II machines.
2. Heat and Pressure
In this method, the dry toner is melted and then flattened by pressure. The pressure is in the form of a belt or roller (where the tension on the hard roller is slight).
The individual particles are discernable and have an overall compact appearance.
Examples: Eastman Kodak 100 and 150 and the Oce 1725.
3. Cold Pressure
Cold pressure is a unique fusion process found on both coated and plain paper machines. The toner is dry and has not been melted by heat.
The pressure is created by a roller, and under magnification, the toner appears as though it could be scrapped off the paper with a scalpel. The identifying factor is the absence of heat.
Example: 3M 839, A. B. Dick 695, and Canon 120.
4. Hot Soft Roller
It is a combination of heat and a soft roller. The soft roller gives the dry toner a textured appearance which is similar to the first application of paint on a wall.
This category is not large, but care must be exhibited during classification so that the presence of a hard roller is not overlooked.
Examples: Xerox 8200 and Gestetner 2002R.
5. Hot Hard Roller
This fusion process melts the dry toner, and the hard roller presses the toner into the paper so the paper fibers are highly visible. Discrete toner particles are not evident but have been melted and pressed into the paper.
Examples: A. B. Dick 7100, IBM 10, IBM Copier III, and Royal 115.
6. Hard Soft Roller
This method is combined with the soft hard roller method. This reclassification resulted from the difficulty in determining which roller was positioned on the bottom during the fusing process.
The toner is fused onto the copy paper as it passes between these rollers, before exiting from the photocopy machine.
If the hard roller is on the top, there will be tracks evident on the surface of the toner. The paper fibers will also be visible.
If the soft roller is on the top, the toner will have a textured appearance. The edge of the toner also helps determine the order of the rollers.
The toner will be slightly flattened if the soft roller is on the bottom. However, if the hard roller is on the bottom, the pressure will flatten the toner into the paper fibers.
Examples: Canon NP-250, Minolta EP- 350Z, Mita DC-213RE and Panasonic FP- 1520.
7. Other Fusion Types
- Blotter: Only applies to liquid toner machines
- Air Dry: only applies to liquid toner machines.
Reference: Crime Laboratory Digest by American Society of Crime Laboratory Directors, FBI Laboratory.