PIGMENT RED 81/ HP RED 2456

C.I.NO.: PR81

Advantage:

Main Application Recommended: Water based inks

Product Description – PR81

HP RED 2456 (PIGMENT RED 81) affords a very clean bluish red shade, The standard magenta on the European Color Scale for letterpress (DIN 16 538) and offset printing (DIN 16 539) is somewhat yellower. For such printing inks, certain high solvent fastness properties are required in order to safely overlacquer the prints. P.R.81 is a strong pigment, which, as with other representatives, is especially true for the PTM types. The pigment commonly darkens noticeably as it is exposed to light. It is recommended used for water based inks.

Recommended Application：

Printing inks: offset inks, water based inks

Technical Data:

• Light fastness: Light fastness rating is assessed on 1 to 8 Blue Wool scale where 1 = ‘Poor’ and 8 = ‘Excellent’.
• Heat Stability : Heat stability values given indicate the maximum temperature at which the pigment can be stoved for 10 min. on the full shade and in reductions without undergoing any significant change in shade.
• Oil absorption: The oil absorption is determined on the basis of EN ISO 787-5 and given in g linseed oil per 100 gm. pigment.
• Solvent bleeding: The bleeding in solvents is tested using the powder grades and the visual rating given on 1 to 5 Grey scale
  where 1 = ‘Heavy bleeding’ and 5 = ‘No bleeding”

Disclaimer — This Technical Data Sheet reflects our best understanding of typical product properties at the time of publication. Listed values are representative of standard production and are not intended as specifications, contractual parameters, or fitness guarantees. Batch variations within normal manufacturing tolerances may occur; users should verify critical parameters against their own requirements before use. Processing methods, formulations, and end-use environments are beyond the manufacturer’s control. The buyer assumes full responsibility for confirming product suitability through its own testing and quality assurance. No intellectual property license is granted or implied. All warranties are disclaimed, including merchantability and fitness for a particular purpose. The manufacturer is not liable for incidental, consequential, or special damages. All sales are governed by the manufacturer’s standard terms, available upon request. This product may contain particles below 0.1 μm. Any user of this product is responsible for determining the suitability of Honor Pigments’s products for its particular application & to ensure that any proprietary rights & existing laws & legislation are observed.

Frequently Asked Questions — PIGMENT RED 81

What water-based ink applications is Pigment Red 81 (HP RED 2456) specifically recommended for?

Pigment Red 81 (HP RED 2456) is specifically recommended for water-based inks used in flexographic and screen printing. According to our technical data, its main application is water-based systems where it delivers a very clean bluish red shade. The product disperses effectively with proper dispersing agents, allowing manufacturers to achieve the high-chroma, fluorescent magenta that standard offset shades (per DIN 16 538/539) cannot match. This makes it ideal for premium packaging, labels, and decorative prints requiring extreme color purity.

How does the color strength of PR81 compare to standard blue-shade reds in offset inks?

PR81 (Pigment Red 81) provides significantly higher color strength and a yellower, more fluorescent bluish-red compared to standard offset magenta shades defined in DIN 16 538 (letterpress) and DIN 16 539 (offset). Our data confirms it produces a very clean bluish-red with extreme vibrancy, requiring careful formulation to avoid overpowering the color balance. For printers seeking the European color scale’s ‘standard magenta,’ PR81 delivers a brighter, more saturated result that exceeds typical offset reds in chroma.

What resistance properties should ink manufacturers verify when using PR81 in high-solvent systems?

For offset and water-based ink applications, PR81 requires verification of high solvent fastness properties to ensure safe overprinting and lamination. Our technical data specifies that for printing inks (offset and water-based), certain high solvent fastness characteristics are necessary. Manufacturers must test resistance to common solvents like ethanol, ethyl acetate, and glycols, as PR81’s xanthene structure can show sensitivity. We recommend pre-testing in the final ink vehicle to confirm bleed resistance and migration stability.

What is the optimal processing temperature range for PR81 in water-based ink production?

PR81 (HP RED 2456) can be processed at heat stability up to 200°C, as indicated in our technical performance data. This allows for normal drying and curing in water-based ink production without degradation. However, due to its sensitive xanthene chemistry, it is advisable to avoid prolonged exposure above 180°C during milling or dispersion to prevent loss of fluorescence. For standard water-based flexo and screen inks operating below 100°C, PR81 offers excellent thermal stability.

Why is the CI Pigment Red 81 (CAS: 81-88-9) preferred over PR122 for fluorescent magenta effects in water-based inks?

PR81 is preferred for fluorescent magenta effects because its xanthene (rhodamine) structure inherently produces a much brighter, more fluorescent shade than quinacridone-based PR122. Our data shows PR81 delivers a very clean bluish-red with intense fluorescence ideal for eye-catching packaging. While PR122 offers superior lightfastness (typical 7-8 vs PR81’s 3-4), PR81’s chroma cannot be matched for applications prioritizing visual impact over weatherability, such as disposable packaging or promotional materials.