Su región e idioma se seleccionaron automáticamente. Puede cambiar esto en cualquier momento en el menú del sitio.
Americas | English

Recubrimientos arquitectónicos

Adiós a los ambientes lúgubres

medición de recubrimientos arquitectónicos

Download PDF

Casas blancas con techos azules. Esa es la imagen popular de la isla griega de Santorini. Hoy en día no sólo son recubrimientos arquitectónicos ofrecidos en “blanco”, sino también en una amplia gama de colores y matices para satisfacer a todos los gustos. No obstante, además de su función decorativa, los recubrimientos arquitectónicos deben aportar determinadas funciones de protección para superficies interiores y exteriores. A fin de cumplir con los criterios de calidad importantes y garantizar la consistencia en la línea de producción, debe establecerse una rutina de control de calidad.

Los recubrimientos arquitectónicos pueden ser utilizados por profesionales o pintores amateur para pintar los edificios y las casas. Los profesionales tienden a ser más sensibles a las características de aplicación, mientras que los propietarios simplemente quieren pintar la pared con el nuevo color, pero aún así desean una pintura para resistir los cambios de color y brillo con el envejecimiento o la abrasión.

Opacity&Classes590x590.jpg

Determinación del poder cubriente

La opacidad es una propiedad importante de la pintura arquitectónica. El poder cubriente de una primera capa de pintura reduce los costos de mano de obra de un trabajo de pintado y es una ventaja competitiva en la promoción de las pinturas para profesionales.

Para una rápida evaluación visual de la opacidad de la pintura esta se aplica, muy a menudo, en cartulinas de color blanco y negro cuadriculado con un rodillo o pincel. A fin de obtener datos objetivos y fiables de reflectancia las mediciones se realizan con un espectrofotómetro.

La opacidad es la capacidad de un acabado para ocultar el sustrato pintado. También se conoce como relación de contraste o poder cubriente. La relación de contraste es definida como la relación entre la reflectancia de película aplicada sobre un sustrato negro idéntico al de una película sobre un sustrato blanco. Opacidad (%) es simplemente la proporción de contraste, multiplicado por 100 para obtener un valor porcentual.
To ensure a smooth and homogeneous surface, the paint is applied to opacity drawdown charts with an automatic film applicator. The charts are made of black and white areas that are large enough to be measured with color instruments having a d/8 measuring geometry. After being dried for at least 24 hours the average of three readings are to be taken on the black as well as the white area.

When using the spectro2guide the opacity value is automatically calculated and displayed on the instrument. Dependent on the results, the coating systems are ranked in four different classes.

In the graph on the right, two differently pigmented wall paints are evaluated. They are applied with 200 μm film thickness. The lower pigmented system shows a significant lower opacity than the higher pigmented paint.

As opacity checks are frequently done it is very important to ensure that the drawdown charts below the paint film are highly consistent in color and gloss. The use of byko-charts drawdown charts guarantees tightest tolerances and prevent erroneous paint batch rejections.
HighLow&References590x590.jpg
Colorant-590x590.jpg

Colorant Compatibility

A colorant sometimes fails to disperse completely in a base paint due to poor compatibility, which can be the fault of the colorant, the paint, or both. This will result in poor color development and can be mainly noticed when high shear forces are applied e.g. application by paintbrush. If there is the tendency for a dark colorant to agglomerate (flocculate) in a paint system, the higher shear application forces the pigments to de-agglomerate resulting in a darker appearance of the color.

A quick test is the so called “rub-up” test. A drawdown with uniform thickness is made on a test-chart. After allowing the paint to dry for a certain time a gentle rubbing action with the finger applies stress to one area of the coating. This tends to disperse the colorants and produces a color difference between the un-sheared and sheared areas of the paint film.

The difference can be measured with the spectro2guide using the total color difference value dE*: The smaller the dE* value the better the color development and vice versa. 
In the above picture a paint system was dispersed from 10 to 120 minutes. The dE* between before and after rub-up is pretty large which means that the pigments tend to flocculate. The use of an additive can improve the stability of the paint system. ASTM D5326 describes a more sophisticated procedure with better reproducibility than the finger rub-out.

Touch up properties
Touch up is the ability of paint to maintain its original appearance when a small area is re-painted with the same paint after the original coat has dried. Small imperfections are often found during inspection of a newly painted wall and it is much less costly if these areas can be touched up instead of having to repaint the entire surface. ASTM D3928 Standard Test Method describes a visual assessment rating for touch up properties. Excellent rating means that there is no noticeable variation in gloss between the touched up and non-touched up area on the panel. A rating of very poor represents a great variation.

The micro-gloss offers an objective way to measure matte to semi-gloss architectural coatings by using the 85° and 60° gloss geometry. The gloss meter can therefore give a clear differentiation between the touched up and non-touched up areas and helps the paint manufacturer to optimize paint properties.
Rating ASTM.jpg
Weather-Stability-590x590.jpg
Weather Stability
Regardless of any environmental influences, color and gloss of interior and exterior walls should remain the same. Weathering studies are routine performance tests to determine durability of paint under extreme weather conditions. The tests are either carried out outside under natural conditions or in the laboratory using accelerated weathering tests. External influences (e.g. solar radiation, moisture, oxygen, and heat) can cause degradation of the colorant and resin. This might lead to changes in color, loss of gloss, embrittlement, flaking, chalking, etc…

Changes in color and gloss are determined by regularly comparing the weathered samples to the original standard. The total color difference dE* is usually recorded. Acceptable changes depend greatly on the hue. Brilliant colors tolerate greater deviations than dark and achromatic colors. In order to obtain additional information about the yellowing, often the db* is documented. The b* value represents the yellow/ blue amount, i.e. the greater the deviation on the b* value, the more the paint yellowed.




UV light absorption can also cause degradation of the bonds of certain polymers used in the paint resulting in a loss of gloss.
spectro2guide is able to measure both color and gloss on the same spot in accordance with international standards.

The graph shows the results of an extreme accelerated weathering test of a blue architectural coating without UV stabilizer. It is obvious that the 60° gloss value rapidly decreases and the color deviations dE*, dL*, and db* increase extremely.
Weather Panels590x590.jpg
Subscribe to our Newsletter and stay informed! subscribe
CANCELAR