Hi,
Sometimes I get e-mails from people that complain that their Retr0brighted parts have gone yellow again over time. Rather than put this in the support thread where it may get lost over time, I thought that if I made it a separate sticky, it may get noticed more.
So, why do the parts go yellow again? It's for a couple of reasons. I shall explain below.
Firstly, I stated in the Wiki that the chemical reaction is reversible; that's why we are able to reverse the yellowing that has occurred over time. The downside of this is that it can also revert back, as it's reversible and can go in either direction.
The second reason is that Retr0bright only treats the surface, it can't penetrate into the plastic where more of the fire retardant is present. Unfortunately, the fire retardant can migrate through the plastic and this is another reason that yellowing can occur again, as more migrates to the surface.
Is there anything that can be done about this? YES, and it's the part of the treatment that most people seem to forget.
Just as the Triangle of Fire needs fuel, oxygen and a source of ignition, the yellowing of the plastics needs three things; The flame retardant, UV light and oxygen - the oxygen is in the air we breathe. Take the oxygen away from both triangles and you don't get a fire and you don't get yellowing, either. How can you do this?
The answer is quite simple. Once the parts have been treated, you should coat the parts in a coat of clear, satin finish acrylic lacquer. This has the effect of cutting off the oxygen supply to the fire retardant and will prevent further yellowing.
For added insurance, you should use an acrylic lacquer that includes a 'UV Blocker' or 'UV Filter'. These products contain a chemical called an 'up-converter', a chemical that has the neat ability to take light in at one wavelength and give it out at another completely different wavelength, in a similar way that fluorescent colours need UV light to make them 'glow'. By shifting the wavelength of the UV light via an up-converter you effectively 'turn off' the UV light, that stops the bromine molecules from vibrating and gaining enough energy to drive the yellowing reaction.
Up-converters are used quite widely in plastics these days for this very reason, however, they weren't used in the master batches back when our machines were built and by using a lacquer containing an up-converter, you are retro fitting the answer to the problem.
This is about as close as you will ever get to a permanent fix for the yellowing problem and I hope that it helps those people who have been disappointed to find that their cherished parts have started to discolour again.
Sometimes I get e-mails from people that complain that their Retr0brighted parts have gone yellow again over time. Rather than put this in the support thread where it may get lost over time, I thought that if I made it a separate sticky, it may get noticed more.
So, why do the parts go yellow again? It's for a couple of reasons. I shall explain below.
Firstly, I stated in the Wiki that the chemical reaction is reversible; that's why we are able to reverse the yellowing that has occurred over time. The downside of this is that it can also revert back, as it's reversible and can go in either direction.
The second reason is that Retr0bright only treats the surface, it can't penetrate into the plastic where more of the fire retardant is present. Unfortunately, the fire retardant can migrate through the plastic and this is another reason that yellowing can occur again, as more migrates to the surface.
Is there anything that can be done about this? YES, and it's the part of the treatment that most people seem to forget.
Just as the Triangle of Fire needs fuel, oxygen and a source of ignition, the yellowing of the plastics needs three things; The flame retardant, UV light and oxygen - the oxygen is in the air we breathe. Take the oxygen away from both triangles and you don't get a fire and you don't get yellowing, either. How can you do this?
The answer is quite simple. Once the parts have been treated, you should coat the parts in a coat of clear, satin finish acrylic lacquer. This has the effect of cutting off the oxygen supply to the fire retardant and will prevent further yellowing.
For added insurance, you should use an acrylic lacquer that includes a 'UV Blocker' or 'UV Filter'. These products contain a chemical called an 'up-converter', a chemical that has the neat ability to take light in at one wavelength and give it out at another completely different wavelength, in a similar way that fluorescent colours need UV light to make them 'glow'. By shifting the wavelength of the UV light via an up-converter you effectively 'turn off' the UV light, that stops the bromine molecules from vibrating and gaining enough energy to drive the yellowing reaction.
Up-converters are used quite widely in plastics these days for this very reason, however, they weren't used in the master batches back when our machines were built and by using a lacquer containing an up-converter, you are retro fitting the answer to the problem.
This is about as close as you will ever get to a permanent fix for the yellowing problem and I hope that it helps those people who have been disappointed to find that their cherished parts have started to discolour again.