Ken -
I am Materials Manager at a plastics company (we make various material handling containers in a variety of colors), so I can explain this to you in detail.
Virgin plastic resin, at least in polypropylene and polyethylene, is typically a foggy, milky color. Colorants are used to die the material to whatever shade it needs to be. These are typically potent colorants where a little goes a long way. We use 33 to 1 color here, which is nowhere near as potent as some, meaning that if we have a 33 pound product, one pound of it is color. This is very similar to how food coloring works for example, and in fact plastics colorants are available in liquid and granular/dry formulations.
I could match that Kenmore gold, the Maytag blue, or any other color with my color supplier. They all have labs and color matchers (usually well paid, scientific technicians who blend market pigments to match a color) who review a sample, and make an offering. Color matching is an art, and a good matcher is usually very well paid.
The fun part about coloring plastics is when a color change is made. If for example Whirlpool was running gold straight vanes, and they needed to change the mold in their injection molding machine to a Roto-Swirl, they would swap the mold, and leave the resin and the color in the machine and it would start making gold Rotos. BUT, in the mid 70s, Sears changed to White Roto-Swirls, so the color would have to get changed to white. But, not before a certain amount of material would have to be run through the machine to purge the system and bleed off the built-up gold color. While this is happening, swirled and mixed products would be made which have blend white and gold together like a tie-die. Eventually the color would go to all white, but not before a number of swirly Roto-Swirls would have been made, which undoubtedly would have gone directly to the grinder.
Speaking of the grinder, these scrap parts can be re-ground and used again along with the resin and color. Often, other items such as processing agents and anti-oxidants (things to stabilize heat processing, mold removal, stability against laundry aids, etc) are added along with. When all of Sears' agitators were gold, there probably wasn't much problem with scrap contamination, same for when they were almost all white, but in recent years, WP has made white, kitchenaid blue, black for commercial Maytags, etc. and these colors cannot be combined without contaminating the color stream. When things do get contaminated, and trust me, they do, the scrap can be turned into something darker, and it all gets masked. We usually do dark gray or black. I am sure that WP puts a lot of scrap/regrind in their black agitators as well.
Plastics can be used and re-used this way, until so many "heat histories" of the plastics being melted and re-molded, that it becomes too weak in properties.
In a nutshell, if WP were to approach a plastics molder to run a gold agitator, or a Maytag blue one, the molder would ask for a color chip or a master, their color supplier would match it, and WP would approve or reject the sample. It is a fairly simple process with an infinite rainbow of color options.
Before anyone asks, if an old agitator mold was found and made runable, yes, your favorite GE ramp agitator or a Maybe powerfin could be molded in bright red, navy blue, or a color to match your machine.
Gordon[this post was last edited: 1/31/2013-16:11]
I am Materials Manager at a plastics company (we make various material handling containers in a variety of colors), so I can explain this to you in detail.
Virgin plastic resin, at least in polypropylene and polyethylene, is typically a foggy, milky color. Colorants are used to die the material to whatever shade it needs to be. These are typically potent colorants where a little goes a long way. We use 33 to 1 color here, which is nowhere near as potent as some, meaning that if we have a 33 pound product, one pound of it is color. This is very similar to how food coloring works for example, and in fact plastics colorants are available in liquid and granular/dry formulations.
I could match that Kenmore gold, the Maytag blue, or any other color with my color supplier. They all have labs and color matchers (usually well paid, scientific technicians who blend market pigments to match a color) who review a sample, and make an offering. Color matching is an art, and a good matcher is usually very well paid.
The fun part about coloring plastics is when a color change is made. If for example Whirlpool was running gold straight vanes, and they needed to change the mold in their injection molding machine to a Roto-Swirl, they would swap the mold, and leave the resin and the color in the machine and it would start making gold Rotos. BUT, in the mid 70s, Sears changed to White Roto-Swirls, so the color would have to get changed to white. But, not before a certain amount of material would have to be run through the machine to purge the system and bleed off the built-up gold color. While this is happening, swirled and mixed products would be made which have blend white and gold together like a tie-die. Eventually the color would go to all white, but not before a number of swirly Roto-Swirls would have been made, which undoubtedly would have gone directly to the grinder.
Speaking of the grinder, these scrap parts can be re-ground and used again along with the resin and color. Often, other items such as processing agents and anti-oxidants (things to stabilize heat processing, mold removal, stability against laundry aids, etc) are added along with. When all of Sears' agitators were gold, there probably wasn't much problem with scrap contamination, same for when they were almost all white, but in recent years, WP has made white, kitchenaid blue, black for commercial Maytags, etc. and these colors cannot be combined without contaminating the color stream. When things do get contaminated, and trust me, they do, the scrap can be turned into something darker, and it all gets masked. We usually do dark gray or black. I am sure that WP puts a lot of scrap/regrind in their black agitators as well.
Plastics can be used and re-used this way, until so many "heat histories" of the plastics being melted and re-molded, that it becomes too weak in properties.
In a nutshell, if WP were to approach a plastics molder to run a gold agitator, or a Maytag blue one, the molder would ask for a color chip or a master, their color supplier would match it, and WP would approve or reject the sample. It is a fairly simple process with an infinite rainbow of color options.
Before anyone asks, if an old agitator mold was found and made runable, yes, your favorite GE ramp agitator or a Maybe powerfin could be molded in bright red, navy blue, or a color to match your machine.
Gordon[this post was last edited: 1/31/2013-16:11]
