Question: Why are there three different types of tomato tiles?
More than 20 years ago, the USDA/ UC-Davis laboratory sold a Tomato Soft Standard. This was a can of processed tomato sauce with calibrated scores. One could purchase this sauce and use it to hitch their colorimeter readings. HunterLab created a porcelain enameled steel tile in a Tomato Red color that closely matched the Tomato Soft Standard color and HunterLab hitched these tiles to the Soft Tomato standard so the customer had no need to deal with the single use Tomato Soft Standard. Instead they could purchase the this tile to use to hitch their instrument.
In 1991 the European Community created a high lead glass glaze on a ceramic backing tile in a red color to mimic a plum tomato. This tile was called the BCR-400 tile. Unique to this tile is that all of the BCR-400 tiles produced were measured on a HunterLab D25 during that 1991 period and calibrated values were assigned. These tiles were put in storage and sold when requested. By 2015 they were no longer available.
As far as future availability of these tiles we have a problem with the EU and EPA and their desire to remove lead and other heavy metals from our existence. The pigments used to create the Red shade for the HunterLab USDA/UC Davis red tile and for the BCR Tomato tile are now banned and no longer available. Existing USDA/UC Davis and BCR tiles are still in use but are no longer sold.
Seeing the need for a Tomato Hitch tile HunterLab had a tile specially formulated to be the closest environmentally friendly match to the no longer available BCR Tomato tile, but it is not an exact match since different pigments are used. We call this tile the HunterLab Tomato tile. All HunterLab Tomato tiles are hitched using a Master CFEZ and have values assigned in HunterLab C/2 coordinates. This insures that these tiles have a common assignment, in the same fashion as the BCR-400.
Please note that since the color is not an exact match there are differences in the L a b values and in the a/b ratio for these tiles.
The purpose of a Hitch tile is to improve agreement between multiple users in different locations using the same type of spectrophotometer. This agreement only occurs when the same type of Hitch tile is used with each spectrophotometer. If one location switches to the new HunterLab Tomato tile, then all other locations that share data will need to switch to the new HunterLab Tomato tile.
The user will notice that due to the different colors of the three type of tiles they have different assigned values. The example below shows the assignment difference between three randomly selected tiles. In this example a sample of 8.5 brix paste prepared, then a single LabScanXE was hitched first to the UC-Davis/USDA tile and the Paste was measured, this was repeated for the other two tiles with the same cup of paste measured for each different hitch. The results show the typical differences a user might expect if they replace their existing tile with a new HunterLab Tomato tile.
8.5 brix Paste measured on LabScanXE
Tile Hitch Values Hitched to the tile described to left
Tile Type L a b a/b a/b TPS
UC-Davis/USDA 28.54 29.23 10.88 2.69 2.47 47.34
BCR-400 25.4 33.3 14.6 2.28 2.06 46.70
HunterLab Tomato 27.7 32.2 13.8 2.33 2.08 46.87