Vulcanized Rubber Stamps
The traditional red rubber stamp that everybody is familiar with will have been manufactured in a vulcanizing press. The first rubber stamp vulcanizing press was patented in 1890 by Charles Schultze in New Orleans USA. Vulcanizing is today one of the most cost effective methods of making rubber stamps for mass produced stamps. Each batch of stamps is produced using a mould. This method of manufacture is more suited to stamp making where the same moulds are used over and over again. Making custom made stamps with a vulcanizing press requiring ‘once only’ moulds will drive the cost of manufacture up Rubber Stamps significantly.
Making the mould – before a mould can be made you must have a master plate manufactured from metal or polymer,Guest Posting the master plate has the necessary relief (the artwork is raised) to make an impression in the mould. Having a master plate made each time a mould is required is what drives up the cost of manufacture for vulcanized stamps. Pressing the master plate into a Matrix board creates the mould that will accept the rubber. Heat and pressure is applied to the master plate and matrix board inside a Vulcanizing press. The Matrix follows the shape of the relief provided by the master plate, this then hardens on cooling.
Making Rubber Stamps – Creating stamps is a simple process once the mould is made. Raw rubber stamp gum is placed on top of the mould and then placed inside the stamp press. Hydraulic pressure is placed upon the rubber and the mould from within the stamp press causing the rubber to melt into the areas of the mould that contain the images and text, curing and hardening takes about 10 minutes. Once cured the sheet of rubber is pulled away from the mould and cut up into individual stamps to be affixed to mounts.
Cost of a vulcanizing system is approximately $12,000 AUD
Advantages – Low cost of production for mass produced stamps, good ink transfer.
Disadvantages – Cost of producing master plates and moulds for custom made stamps.
Laser Engraved Rubber Stamps
The traditional raw rubber used for vulcanizing stamp dies is quite unacceptable for the production of laser stamp dies, the laser process requires a very even thickness and blemish free surface to produce an acceptable printed image from a stamp die. The rubber must also be subjected to a specific curing process before it can be exposed to the elevated temperature of a laser beam.
The depth of the engraving is determined by the laser speed, its wattage and the density of the rubber. For example, a 50 or 100W engraver will engrave the rubber deeper and faster than a 25W machine, which may require a second pass to achieve a similar result. Usually supplied in an A4 size sheet form, a good quality laser rubber is required for engraving stamp dies and must also have suitable compression strength and ink transfer properties.