Top 5 Ways to Help Improve Back-Painted Glass Opacity
Back-painted glass applications require glass paint to block light transmission and create an opaque result so learn these ways to help improve back-painted glass opacity.
Glass fabricators know that without opacity the glass remains semi-translucent or transparent. This is considered a failure in Architectural or Decorative Glass applications. In other words, an opacity failure is when light transmits through the painted glass surface revealing the material, adhesives and supporting structure that is intended to be hidden or concealed.
What is Opacity?
Opacity, as it relates to Glass Paint, describes the “hiding strength” or “concealing power” of paint. Opacity on glass is achieved by applying a light-blocking layer on surfaces 1 or 2.
The Supreme Paint co provides this clarification:
The hiding strength (or opacity) of paint is largely influenced by the difference of the refractive indices of the pigment and the medium, particle size and dispersion of the pigment (i.e. particle shape and degree of aggregation of the particles), the proportion of pigment in the vehicle (i.e., pigment volume concentration or PVC) and the thickness of the applied film. These factors determine the opacity of a particular paint.
We know that there are 3 main factors affecting Glass Paint Opacity:
The glass paint colour
The thickness of the paint applied
The quality of paint used
How does Colour affect Opacity?
The easiest colours for back-painted glass to achieve opacity are white and black using our Glass Paint Technology water-based product.
Our white bases contain white titanium dioxide which has a very high opacity rating.
Some colours have a lower opacity like yellow, pink, red and orange.
These low-opacity colours require a different application approach.
How does Paint Thickness affect Opacity?
The naturally higher opacity paints like grey and black only require a +/- 4 mil coating or one coat.
Most of the lower opacity colours require 6 to 9 mils (one to two coats) to reach acceptable opacity.
Thicker coatings increase costs in materials used and labour to apply.
Does the Quality of the Glass Paint affect Opacity?
High-quality formulas require more expensive components.
A higher ratio of white titanium dioxide increases the cost of the glass paint but often reduces the thickness of the coating required to reach acceptable opacity.
Here are the Top 5 Ways to Help Improve Back Painted Glass Opacity
What are the Opacity Implications of the Color we are using?
We know that lighter colours (like yellow, pink, red and orange) may require more coats.
Using a high-quality white base will help improve opacity.
Dark colours like Black, Grey and Brown provide opacity with a thinner coating.
What is a Backup Coating and how does it Improve Opacity?
A backup coating offers a glass paint layer that creates opacity.
Our backup colour is a dark grey colour used on the back of brighter (low-opacity) colours.
For example, if you are applying a bright yellow colour, instead of painting 3-4 coats to hopefully create opacity, you can do 1-2 coats of yellow and 1 coat of grey.
The grey backup paint not only creates great opacity with less paint, but it will also protect the yellow coating from scratches and abrasions during transit and installation.
The colour on surface two remains true and accurate, while the grey on the back will only be seen on the coating side.
When using a backup grey always make sure you apply enough of the desired colour down first, so the grey doesn’t leak through the coating side.
Test your coating coverage by placing the glass flat on a table, paint side down. Look for pin holes or light spots in the coating. If the colour looks true and even, you know it is ready for backup grey coating.
Please let us know if you have any questions about this, we can help you with the best grey colour for this application.
Does the Back Painted Glass installation location affect Opacity?
If the Back Painted Glass is to be installed on a wall in a brightly lit area you will need to be more sensitive to the glass paint opacity.
Opacity weakness is often revealed when using black silicone adhesive to secure the back-painted glass to a wall.
When the adhesive is darker than the paint colour, opacity is not 100% and the environment is brightly lit there is a risk that the adhesive will create dark spots.
As mentioned earlier, when you recognize these conditions you may choose to apply a thicker coating or add a backup grey.
What tools are available to ensure the desired Glass Paint Thickness?
There are several tools available to create consistency in your paint thickness.
Ensuring you apply a thick enough coating to create an opaque finish is one of the most important ways to help improve back-painted glass opacity. It is also important to know how thick you are applying the paint so as to not over or under-apply.
Over-applying is one method to ensure opacity, however, you don’t want to waste paint either.
Here are a couple of instruments that help you find out how thick you are applying your paint:
Wet Film Thickness Gauge
The Wet Film Thickness Gauge is very simple yet very effective. Using the teeth on the outside of the instrument, you simply apply those to the freshly applied paint and depending on which teeth mark it touches, that is how thick you are applying the paint.
Dry Film Thickness Gauge
The Dry Film Thickness Gauge is used for the same purpose as a wet film thickness gauge, to understand how thick the cured coating is.
The only difference between the wet and dry film gauges is that a wet film thickness gauge can only be used during production. While the dry gauge can only be used in post-production.
This tool is a little more advanced to deliver accurate results.
However, it is important to know that the thickness will be different from wet vs dry. During the curing process, the coating will lose thickness and be much thinner once dry.
Who Offers a High Opacity Glass Paint for Back Painting?
It is important to understand the formula strengths and weaknesses of Architectural and Decorative Glass Paint for back painting applications.
Here are some key metrics to look for as you make your Glass Paint vendor selection:
Formulas vary from manufacturer to manufacturer and so does the Opacity strength.
Some formulas can work with a higher percentage of colourant but the adhesion is weakened,
Some formulas include more high-quality ingredients and less filler.
Glass Paint Technology has invested in a higher quality formula that creates a more opaque coating even with lighter colours AND we can accomplish the desired opacity with less paint!
In fact, GPT works with companies to achieve the required opaqueness, especially on large runs where anything other than 1-2 coats is unacceptable.
And we have gained a lot of experience learning ways to help improve back-painted glass opacity while working with roll coaters, curtain coaters and automated or hand spray applications. We have seen it all!
So please Contact Us today to discuss your opacity concerns and learn how we can help you.