What Tomato Tiles are available as Hitch standards?

There are two Tomato Tiles in general use – the European BCR-400 Tomato Tile and the American USDA/UCDavis Tomato Tile. Both are “tomato red” in color but visually different.

The BCR-400 Tomato Tile was designed to be similar in color to Italian plum tomato paste/purée while the USDA/UCDavis Tomato Tile is the color of tomato paste from field tomatoes.

The purpose of both Tomato Tiles is the same – to be a hitch standard for instruments in the localized tomato red area of color space so that inter-instrument agreement is optimized for various processed tomato products like tomato paste/purée, sauce, juice and catsup. As a CRM (Certified Reference Material), the BCR-400 Tomato Tile is intended for hitching or instrument performance qualification purposes only. It does not represent a specific color quality for tomato paste.

This BCR Tomato Paste Tile was designed to match the color of ripe plum tomato paste and manufactured by Ceram Research UK. Around 1996 CERAM Research sent 1100 clay-based “tomato red” tile standards to the Community Bureau of Reference (BCR) in response to requests from the European Community and measured them for BCR who in turn issues tile labels and certificates.

Assigning Authority for the BCR-400 Tomato Tile

BCR/IRMM – Institute for Reference Materials and Measurements, Geel B-2440 Belgium irmm.jrc.be search on “BCR-400 TOMATO PASTE COLOUR TILE”

The Community Bureau of Reference (BCR) is now called the Institute of Reference Materials and Measurements. The IRMM is the research center of the Commission of the European Communities, and functions as a primary standards body supplying BCR, IRMM and ERM certified standards for the European Community similar to the standard reference materials supplied by NIST (National Institute of Standards and Technology) in the United States.

Information on Tomato Paste Colour Reference Tile BCR-400 from the IRMM Web Site:

The BCR-400 consists of a 100 mm x 100 mm (4 in x 4 in) red ceramic tile calibrated with Hunter L, a, b C/2 values for a 45°/0° or 0°/45° viewing geometry, illuminant/standard observer C/2° and an aperture of 50 mm nominal diameter. BCR does the assignment of the BCR400 Tile values. If other color data values such as a/b ratio are needed these may be calculated readily from the assigned color values.

FAQ: “Who assigns the Hunter L, a, b C/2 color values to the BCR-400 Tomato Tile?”

Typical Hunter C/2 color values of the BCR-400 Tomato Tile are:

L = 26, a = 33 and b = 14.5 C/2

Each tile is individually assigned by IRMM with overall assignment uncertainties in Hunter L, a and b values being ± 0.2, ± 0.3 and ± 0.1 respectively per reference certification document:

M. Kent, F. Malkin,  J.F. Verrill, D.J. Henshall; The Certification of a Tomato Paste Colour Reference Tile CRM 400 published December 31, 1991 by European Communities Union (EUR-OP/OOPEC/OPOCE)

USA Sources for the BCR-400 Tomato Tile

While you can contact IRMM directly above, the BCR-400 Tomato Tile is more readily available from:

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HunterLab, Reston, VA USA hunterlab.com

HunterLab offers the BCR-400 Tomato Tile (L02-1014-594) with a statement of assigned values and traceability, along with the reference document on CD. Orders can be shipped quickly and worldwide.

RTC, Laramie, WY 82070 USA rt-corp.com

RTC is a distributor of certified reference materials including European Union IRMM, BCR and ERM standards such as the BCR-400 Tomato Paste Color Reference Tile. Search on “BCR-400”.

European Sources for the BCR-400 Tomato Tile

Sigma-Aldrich, CH-9471 Buchs, Switzerland www.sigmaaldrich.com

Sigma Aldrich is a distributor of certified reference materials including European Union IRMM, BCR and ERM standards. Search on “BCR400 TOMATO PASTE COLOUR REFERENCE TILE (colour values)”

FAQ: “What if a client needs to get a BCR-400 TOMATO PASTE COLOUR TILE re-certified?”

A recalibration service is not available from IRMM. The client is advised just to purchase a new BCR-400 tile from HunterLab (L02-1014-594 BCR-400 Tomato Tile). A follow-up question is how often should the tile be replaced? The IRMM certificate that comes with the BCR-400 Tomato Tile is not specific suggests that “the certificate is valid for 5-years after purchase” if kept covered and out of direct sunlight. Much depends on how well the tile has been cared for but a 5-year term is reasonable.

FAQ: Crazing on the BCR-400 Tomato Tile

“Our customer received a new BCR-400 Tomato Tile and says that some kind of crack in the tile causing wrong measurements outside specification. I have checked his ColorFlex EZ Tomato sensor – white tile and green tile repeatability/sample-monitor signal levels are all good. Can you tell what the problem is.”

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What this customer is seeing is something called “crazing” – a pattern of very fine lines in the finish of the BCR-400 Tomato Tile. It is present and normal in all clay-based tiles and well described in wikipedia as follows:

“Crazing is a spider web pattern of cracks penetrating the glaze. It is caused by tensile stresses greater than the glaze is able to withstand. Common reasons for such stresses are: a mismatch between the thermal expansions of glaze and body; from moisture expansion of the body; and in the case of glazed tiles fixed to a wall, movement of the wall or of the bonding material used to fix the tile to the wall.”

We only see crazing on clay-based tiles like the BCR-400 Tomato Tile; our other porcelain-on-steel tiles do not have this finish effect.

FAQ: “I just replaced my BCR-400 Tomato Tile. What do I do with my old BCR-400 Tile?”

An old BCR Tomato Tile can be confused with the new one. You should only be hitching to one BCR-400 Tomato Tile at a time and it should be the newest one.

One good alternative use of an old BCR-Tomato Tile is to use it as a PQ (Performance Qualification) check prior to sample measurements.  This allows operators to verify that the instrument is set up and reading correctly for tomato color.

  1. Hitch the instrument to the new BCR-400 Tomato Tile and read back this tile to verify that the hitch has been implemented correctly. The read values (Hunter L, a, b C/2°)  should match those on the back of the new BCR-400 Tomato Tile. Put the new Hitch BCR-400 Tomato Tile away in a safe place.
  2. Strip the label off the back of the old BCR-400 Tomato Tile.
  3. Read the old BCR-400 Tomato Tile and baseline this tile in metrics used to measure your samples. These can be Hunter L, a, b C/2° color values but also a/b ratio or Processed Tomato Scores. Make up a label with these baseline values, a baseline date and a signature of the person who did the assignment.
  4. Every day prior the sample measurements, standardize the instrument and read the old BCR-400 Tomato Tile as a PQ (Performance Qualification) check. The values read should closely match the baseline values.
  5. If an operator does not read that BCR-400 PQ Tomato Tile closely to the baseline values:
  • First clean all tiles, re-standardize and re-read the PQ BCR-400 Tomato Tile again. This usually clears the issue.
  • If  the PQ BCR-400 Tomato Tile is still not reading closely, read the Hitch BCR-400 Tomato Tile and verify the instrument reads the assigned Hunter L, a, b C/2 values. If not, re-set the hitch; verify the hitch and PQ read back.
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FAQ: “As all of my customers are using BCR-400 Tomato Tiles, I just replaced my older USDA/UCDavis Tomato Tile with the BCR-400. What do I do with my old /UCDavis Tomato Tile?”

While it does not have good flight characteristics, you could consider making a frisbee out of it. The key point is that if you do not plan to use it as a tomato hitching standard in the future, you need to remove it to avoid confusion with the BCR-400 Tomato Tile. One good use is to consider making it a PQ (Performance Qualficiation) Tile as described above.