Previous official color standards for maple sirup, designated Light Amber, Medium Amber, and Dark Amber, were solutions of sugar caramel in glycerin standardized in terms of transmittance at 560 mμ. These solutions were not satisfactory because of instability of color and inconvenience of repeated preparation. Glass color standards were accordingly developed to match the chromaticities of fresh standard solutions in 31.5 mm depth. An improved color comparator was devised for use with the glass standards. The caramel-glycerin solutions and maple sirups were characterized spectrophotometrically and in terms of several one-dimensional color scales in use in the sugar industry. Complete specifications for the standard solutions and new glass standards are presented in the CIE system. Color tolerances were established in MacAdam units of chromaticity difference and a simple one-wavelength method of testing glasses for the production of duplicate standards was developed.

Genevieve Reimann, Deane B. Judd, and Harry J. Keegan J. Opt. Soc. Am. 36(3) 128-159 (1946)

References

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Specifications for former caramel-glycerin color standards for maple sirup, and characterization of two sets of solutions I and II prepared for present investigation.

Balch, references 3 and 4.
Balch, “corrected to master standard by means of calibration chart furnished by the manufacturer.”
Prepared to give transmittancy specified by Balch.
Directly in terms of the primary wedge in standard instrument at Munsell Color Company, Baltimore (B.A.B. 1953).
Color Index of maple sirup, Porter et al.13
Color Index of filtered sugar solution when multiplied by 1000/c, where c is concentration of sugar, g/ml. See page 276 of reference 14. For maple sirup c=0.863 g/ml.
Compensated Color Index of sugar solutions when multiplied by 1000/c, Gillett.14,15 Q ratio, Peters and Phelps.8–16.
Slope of logA νs logλ curve, here calculated as (1/0.049) log(A_{500}/A_{560}). See page 260 of reference 8.
CIE data based on 1931 standard observer and Illuminant C, for 3.15 cm thickness of solutions (compensated for solvent).

Table II

Attenuancy ratio and wavelength exponent (slope of logA* versus logλ curve) for caramel-glycerin solutions and maple sirups of different origins.

Liggett and Deitz.8
Calculated as Δ logA*/Δ logλ for wavelengths 500 and 560 mμ.

Table III

Chromaticity difference, in MacAdam units ΔS, between “standard” caramel-glycerin solutions I and II and master set of glass standards selected to match chromaticities of solutions I (3.15 cm of solution compensated by equal thickness of glycerin).

Calculated from averaged x- and y-values, Table I.

Table IV

Specifications and colorimetric analysis for master set of glass color standards for maple sirup. CIE data are based on 1931 standard observer and Illuminant C.

For testing thick component (4.04 mm), thin component (3.41 mm), and finished combination, respectively. $\mathrm{\Delta}S=[{g}_{11}{(\mathrm{\Delta}x)}^{2}+2{g}_{12}\mathrm{\Delta}x\mathrm{\Delta}y+{g}_{22}{(\mathrm{\Delta}y)}^{2}{]}^{{\scriptstyle \frac{1}{2}}}$ $\mathrm{\Delta}E=50\{{(0.23{V}_{Y})}^{2}+[\mathrm{\Delta}({V}_{X}-{V}_{Y}){]}^{2}+[0.4\mathrm{\Delta}({V}_{Z}-{V}_{Y}){]}^{2}{\}}^{{\scriptstyle \frac{1}{2}}}$ $\mathrm{\Delta}C=1000[{(\mathrm{\Delta}x)}^{2}+{(\mathrm{\Delta}y)}^{2}{]}^{{\scriptstyle \frac{1}{2}}}$

Tables (6)

Table I

Specifications for former caramel-glycerin color standards for maple sirup, and characterization of two sets of solutions I and II prepared for present investigation.

Balch, references 3 and 4.
Balch, “corrected to master standard by means of calibration chart furnished by the manufacturer.”
Prepared to give transmittancy specified by Balch.
Directly in terms of the primary wedge in standard instrument at Munsell Color Company, Baltimore (B.A.B. 1953).
Color Index of maple sirup, Porter et al.13
Color Index of filtered sugar solution when multiplied by 1000/c, where c is concentration of sugar, g/ml. See page 276 of reference 14. For maple sirup c=0.863 g/ml.
Compensated Color Index of sugar solutions when multiplied by 1000/c, Gillett.14,15 Q ratio, Peters and Phelps.8–16.
Slope of logA νs logλ curve, here calculated as (1/0.049) log(A_{500}/A_{560}). See page 260 of reference 8.
CIE data based on 1931 standard observer and Illuminant C, for 3.15 cm thickness of solutions (compensated for solvent).

Table II

Attenuancy ratio and wavelength exponent (slope of logA* versus logλ curve) for caramel-glycerin solutions and maple sirups of different origins.

Liggett and Deitz.8
Calculated as Δ logA*/Δ logλ for wavelengths 500 and 560 mμ.

Table III

Chromaticity difference, in MacAdam units ΔS, between “standard” caramel-glycerin solutions I and II and master set of glass standards selected to match chromaticities of solutions I (3.15 cm of solution compensated by equal thickness of glycerin).

Calculated from averaged x- and y-values, Table I.

Table IV

Specifications and colorimetric analysis for master set of glass color standards for maple sirup. CIE data are based on 1931 standard observer and Illuminant C.