The demand for granites with vivid colors has been growing in the ornamental stone market, with a preference for granites with high weathering, commonly known as yellow granites.
These granites are yellowish/brown in color, as a result of natural weathering/oxidation processes, as opposed to the healthier granites that have a light color.
Portugal has a great diversity of granites with this color (gray), making it relevant to create techniques that allow accelerating the natural weathering process.
The investigation carried out sought to identify the best oxidation/color techniques for various varieties of Portuguese gray granites.
The products used make it possible to obtain granites with yellow/brown color, similar to the natural color of oxidized granites.
In addition to these obtained colors, it is also possible to obtain pink tones.
The process used allows for a gradation in the intensity of the color to be obtained.
The staining of granites from iron shot is possible when the samples are submitted to specific environmental conditions and in a certain period of time. When compared to previous methods, this process needs a longer period of time.
However, unlike the previous method, handling care is much lower and the reuse of the product in question becomes possible. From this process it is possible to obtain orange colors, homogeneous or forming patterns, on the surface to be colored.
After the coloring/oxidation process, it is necessary to test the durability and resistance of the products used.
The use of the spectrophotometer makes it possible to calculate the chromatic variation (∆E) over time, providing information about the durability and effectiveness of the products used and the environmental situations in which granites can be applied without significant modification of surface characteristics.
The samples selected for analysis of chromatic variation were placed outdoors, where they are exposed to meteorological agents.
In addition to these, the samples are occasionally watered allowing to assess a color evolution over time.
This evaluation is done every 90 days, thus allowing to observe the loss or gain of color in the elapsed time.
The technique developed allows the process to be carried out in delimited areas of the plates, which opens up a huge field of evolution in the design of made-to-measure pieces, with graphics and colors tailored to customers.
Subscribe our newsletter
