A previous a post on the forum - http://www.dyesubforum.co.uk/vbforum/sh ... page11#107 - suggested that it would be of interest to perform an Extreme Dishwasher Test on dishwasher-safe mugs to determine how resilient they are to dishwashing.
I recently undertook the test, using a procedure similar to that shown on this website - http://www.cupsandstuff.com/quality.asp - using four different mugs I had available to me.
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Test Procedure
To summarise, the test involves immersing the mugs in a dishwasher-tablet water solution at boiling point for one hour. This is very much an "Extreme Dishwasher Test". The reason that I call it "extreme" is as follows:
Domestic dishwashers typically run at 55°C - 75°C and spray jets of water onto the items. 75°C is reached during a sanitising cycle during the final rinse (the temperature rises until the thermostat trips, so this is a very short process). Newer detergents require lower water temperatures (55°C-60°C) otherwise the cleaning enzymes break down at the higher temperatures. According to their website, 51°C - 60°C should be used with Finish Powerball tablets (Gelpacs, powder, and gel are used at 60°C).
This extreme "pan" test immerses the mugs in a saucepan of boiling water (100°C) for a full hour. The mugs are constantly in contact with the dishwasher tablet solution for the duration of the test. Not only does a domestic dishwasher never reach this temperature but the mugs are not fully immersed in the solution for this length of time.
So, to be perfectly clear, this "pan test" is very much an Extreme test. Should a mug survive this, it should survive anything. If it fades just a little bit, it should still survive anything. If it fades a lot, just be aware of how much faith you want to put in it.
(As I don't have a dishwasher myself, I'm relying on the internet for how a dishwasher works.)
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Results
The following photos reveal the results of my test. If the mugs look "darker" at the top of the print, it's because the water solution did not completely cover the mugs and so there is less fading towards the top of the mug.
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Click here for larger image.
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Comparison: Non-Dishwasher Mug

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Comparison: Orca-coated Mug

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Comparison: Coralgraph Mug

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Comparison: RN-coated Mug
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Conclusions
Due to the extreme nature of this test, all mugs faded to a certain degree. The fading on the Orca mug shows colour shift and a blurring of the print. The Coralgraph and RN-coated mugs look very similar to each other. The slight fading on the Coralgraph/RN mugs hasn't affected the sharpness of the print nor has the colour shifted (the print just looks "brighter"). These are clearly the most resilient mugs in the test, which is as expected. Comparing close-up, the Coralgraph mug just pips the RN-coated mug, but the difference is small.
I don't know what coating is used on the Coralgraph mugs, but it's clearly up there with RN-coated mugs. The RN-coated mug is either from BMS or Listawood - I can't tell which, except that it printed with the "white spot" issue that was more common with BMS mugs a year ago than with Listawood mugs.
This non-dishwasher mug used in the test is from a supplier that isn't around anymore and it was described by that supplier as "dishwasher safe", not "dishwasher proof" (the difference being that their definition of "dishwasher safe" would survive a couple of dishwasher cycles but not constant washing as the "dishwasher proof" ones would).
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Further Information
Prior to this extreme test, I did a "real world" test back in 2008. The "real world test" used three typical mugs placed in the back of a domestic dishwasher for 30 days, and the dishwasher was used every day. The results can be seen on my site, here: http://www.mugsandgifts.co.uk/dishwashing-mugs.
After the "real world test", the same "non-dishwasher" mug looked like this:
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[/CENTER]Despite the fading, there's still quite a bit more of the ink left on the mug than the same mug used in the "extreme" test. This underlines that the extreme test is, indeed, pretty extreme.
I hope someone finds the results of this test of interest.
