Instrumental Color Measurement Makes the Most of Ammonia Fuming

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Posted on February 23, 2016

The Advantages of Ammonia Fuming

Hardwood flooring has traditionally received its final color using a variety of staining products that use pigments and dyes that cover the surface with a translucent coating of color and give homeowners a broad spectrum of options to create the look they want. Despite the versatility of staining, this coloration process has a number of disadvantages, including vulnerability to blotching, color loss over time, and potentially obscuring the grain of the wood. The staining process itself requires careful preparation to ensure an even appearance and protect against accentuation of imperfections. What’s more, because the stain primarily sits on top of the wood and does not penetrate deep into the material, scratches and scrapes can easily reveal the natural color of the wood beneath the surface, creating an unattractive and worn appearance.

In contrast to staining, ammonia fuming is not simply a superficial coloration method, but a deep-penetrating chemical reaction. As noted by researchers Petr Čermák and Aleš Dejmal, “Changes in color are due to the reaction of ammonia with tannin in the wood and atmospheric oxygen.”1 Commercial fuming takes places in a sealed chamber in which the wood is exposed to an ammonium hydroxide solution that darkens the wood, reaching as deeply as 1” on the end grain and between 1/16” and 1/8” on the face grain.”2 As a result, the wood may be cut and lightly sanded or planed following fuming and normal wear and tear, scratches, and scrapes are far less likely to reveal untreated wood, preserving a pleasing aesthetic appearance. Additionally, the fuming process allows the natural wood grain to show because it is not covered by a layer of dye or pigment. The final result is a distinctive, durable flooring product with a character and beauty many consumers prefer.

Spectrophotometric Evaluation of Ammonia Fuming

While the ammonia fuming process corrects for many of the problems associated with wood staining, it can have its own drawbacks. Most notably, ammonia may react to different boards in different and unpredictable ways, creating an inconsistent appearance. While many consumers prize this variation and see it as part of the inherent charm of fumed hardwood floors, increasing consistency both within a batch and between batches allows manufacturers the opportunity to create more harmonious products and gives contractors the ability to more accurately match boards for replacement at a later date.

Spectrophotometers are uniquely suited to evaluate hardwood floor color owing to their advanced colorimetric technologies. Instruments with integrated height measurement automatically compensate for height variation to obtain accurate color measurements of textured surfaces and can easily account for gain, knots, and handscraping. Simultaneously, color averaging gives operators the ability to precisely capture color information despite naturally occurring color variation within each board. As such, virtually all research into the color effects of ammonia fuming uses spectrophotometric instrumentation to quantify color and correlate color change with variables such as duration of treatment, temperature, and extractive, nitrogen, and tannin content.3 Incorporating spectrophotometers in the fumed wood production process allows manufacturers to monitor color change during the treatment process to determine when floor boards have reached their desired hue. By eliminating the subjectivity of the human eye, operators can be detect the precise point the board enters the chosen color standard and identify out of spec product. Pairing your spectrophotometer with sophisticated software allows you to evaluate ammonia fuming process variables by creating reliable datasets that may be used to immediately tailor treatment processes as well as archiving historical data for future reference.

Full article with photos available here:

https://www.hunterlab.com/blog/color-measurement-2/instrumental-color-measurement-makes-the-most-of-ammonia-fuming/

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