Just Paint 4.Pmd

JUST PAINT Published by GOLDEN Artist Colors, Inc. / Issue 4 Taming the Foam Monster in Acrylic Paint! One of the most critical problems in the manufacture and use of acrylic paint is the development of foam. It can cause structural problems in the dry paint film by weakening it and can create a more permeable paint surface capable of imbibing dirt and other discoloring pollutants. But the primary problem with foam is that it can cause a clouding or fogging in an otherwise transparent acrylic surface. Understanding how foam is created leads to an understanding of how to deal with and potentially avoid it. While it is easy to suggest not to create foam in the first place, this is sometimes difficult to achieve with waterborne acrylics. No matter how careful one is with their working tech- nique, the simple movement of a paint filled brush rising with high points on the work and slapping down into valleys is INSET: Detail of foam generated from enough to create a dried cloud of foam. inappropriate use of acrylic polymer as a topcoat. This is usually only a problem when working in transparent layers or applying a transparent coat of varnish. quires different levels and types or combina- The Source of Foam tions of surfactants to make a stable paint. of heavy bodied acrylics. Thinner bodied Foam generation in waterborne While it is sometimes possible to substitute paints, like Golden Fluid Acrylics, require a acrylic paints and mediums comes from a lower foaming product, it is important much more delicate defoamer to avoid several sources. Yet, all of these have, as not to sacrifice overall paint other film defects that too much or too their primary basis, the use of chemical performance. strong a defoamer can cause. Shaking or wetting agents called surfactants. From the Creating foam is usually an unavoid- strong agitation of these colors during mix- same family of chemicals as detergents, sur- able consequence of the high speed mixing ing may cause a froth of foam like the head factants tend to be extraordinar- and shearing processes required of a beer. ily good at creating foam. How- ▲ to disperse pigments and make Foaming in Varnish ever, they are indispensable. By paints. Chemical defoamers, It has been the practice of many SURFACTANTS which act to both reduce foam reducing the surface tension of TEND TO BE artists and paint companies to recommend water, they serve to stabilize the EXTRAORDINARILY generation as well as break foam using polymer medium as a varnish for acrylic polymer, and are also re- GOOD AT structure once it occurs, are part acrylic paintings. We have seen many cases quired for dispersing pigments CREATING FOAM. of every waterborne paint for- where this has caused irreparable foam into the acrylic. HOWEVER, mulation. Thicker paints allow damage to the surface of the painting. It is Optimizing surfactant use THEY ARE for the incorporation of stronger nearly impossible to apply a layer of poly- INDISPENSABLE. defoamers, yet the thicker the is the most complex and critical ▼ mer medium without creating foam, which part of paint formulation. Their paint, the more resistant the will not dissipate and is not removable. For high propensity for foam genera- foam is to dissipating. It may this reason we recommend using Golden tion requires tight controls. Each take up to several weeks or Soft Gel (Gloss) if an isolating coat is pigment, each system, each material, re- months for foam that is stirred in to rise out needed or when strong defoaming is Continued back page... Just Paint / Issue 4 2 WILL CADMIUM ALWAYS BE ON THE PALETTE? ALTERNATIVE PIGMENTS ARE BECOMING AVAILABLE! Environmental and health concerns Cadmium pigments excel in high heat In the industrial setting of the paint have spurred increasingly stringent regula- applications, as encountered in the glass and manufacturer, where inhalation of dry pig- tory requirements for the use and disposal injection plastics industries. Although the ment is much more likely, the Occupa- of Cadmium based pigments. As a result, performance of cadmium pigments in the tional Safety and Health Administration many industries have decreased or entirely glass industry may be (OSHA) regulates eliminated the utilization of these unequaled, their use all cadmium com- colorants. If these trends continue, formu- is prohibited to a pounds and has set lating cadmium pigment into artist paints large extent due to stringent workplace will become increasingly difficult, and ulti- the “Toxics in Pack- exposure limits and mately, may be impossible due to lack of aging” laws of many hygiene require- availability. However, the introduction of states, which limit ments. OSHA’s newer organic pigments has made finding the intentional addi- permissible exposure suitable alternatives easier than ever. While tions of heavy metals limit for cadmium not identical to cadmium based pigments, to packaging materi- exposure through their properties are similar enough in some als. Glass is manufac- inhalation is 5 mi- respects, and superior enough in others, to tured primarily as a crograms per cubic warrant consideration. Golden Artist Col- packaging material. Cadmium Pigment Usage in North meter of air ors has recently introduced three such col- These restrictions breathed. In an 8 ors; Hansa Yellow Opaque, Pyrrole Red have also impacted plastic packaging, but hour workshift, approximately 9 cubic Light, and Pyrrole Orange. Also in this not applications known as “engineered res- meters of air are breathed. Workers ex- group is Pyrrole Red, which was first made ins” which encompass such uses as injection posed to cadmium approaching this level available by Golden in 1990. molded handles and housings for lawn and are required to have periodic testing to Cadmium pigments were discovered power tools. These are high heat applica- determine their blood levels of the ele- around 1820 and first commercialized for tions where the cadmium pigments continue ment. artists’ use by the mid 1840’s. Although to outperform organics due to their heat There are also concerns regarding Claude Monet used them extensively in the stability. the long term environmental impact of 1840’s and 50’s, the scarcity of the metal Another industry which has declined cadmium in landfills. These are largely the kept their use relatively limited in artists drastically in cadmium pigment use is auto- result of the use of soluble cadmium com- materials until the 1920’s. Their introduc- motive manufacturing. Whether it is a mat- pounds in battery manufacture and the tion provided unequaled hues in the yellow ter of color fashion, with earth tones favored proliferation of spent batteries in the waste to deep red range, in terms of brightness over a bright red interior, or a response to stream. However, for the purposes of re- and lightfastness. increased regulation, industry sources report ducing the potential for cadmium com- While cadmium pigments are con- that cadmium pigment use has been all but pounds leaching out of landfills, cadmium sidered extremely lightfast under conditions eliminated. from all sources is of concern to the agen- of indoor use and exposure, they fade a Toxicity and Environmental Impact cies regulating waste disposal. Any cad- great deal when used outdoors in acrylic Animal studies have shown that cadmium-containing waste that leaches levels paints. For this reason, they should not be mium pigments are potential carcinogens of the metal greater than 1 mg/liter in the used in exterior mural painting. The differ- when inhaled, which is why they carry the Environmental Protection Agency (EPA) ence between indoor and outdoor perfor- warning, “do not spray apply”. They are not Toxicity Characteristic Leaching Proce- mance is thought to be due to the combi- believed to be toxic by ingestion if they are dure test method is considered hazardous nation of environmental factors encoun- of low solubility as determined by laboratory waste. This is a rigorous acid solubility tered outside; moisture, ultraviolet radia- testing. Over the years, pigment manufac- test which some cadmium pigmented art- tion and air. These cause bleaching induced turers have produced cadmium pigments of ists paints will not pass. In recent years, by oxidation of the cadmium sulfide to progressively lower solubility of both the numerous states have passed additional cadmium sulfate. That is why the water cadmium and selenium in efforts to increase regulations designed to reduce cadmium permeable acrylic vehicle is prone to this safety. The solubility tests are designed to entering the waste stream from the pack- effect, while cadmium pigments used in mimic the pH, temperature and agitation aging and printing industries, regardless of impermeable binders, such as rigid plastics, that would be experienced in the stomach. solubility. are not. However, detractors from this theory cor- Periodically, bills are introduced in Industrial Use rectly point out that there are other mecha- state legislation that would prohibit uses Only 5-7% of total cadmium pig- nisms at work in the body and that these of cadmium in consumer products. In ment production is used in the manufacture analyses should not be considered entirely Minnesota, a bill to this effect was passed of artist materials. Since most is used else- conclusive. Therefore, while use of low for ink, paint and dye products, but did where, clues to future availability may be solubility cadmium pigments diminishes contain an exemption for art materials. found by looking at what is happening with their toxicity, there is still reason to treat Similarly, in Europe, art materials enjoy an the higher use industries. paints made with cadmium pigments with exemption from prohibitions of cadmium extra care and to seek alternatives. use in consumer products. Continued page 5 Just Paint / Issue 4 3 Product Review: glossy. Each color’s sheen and degree of opacity Acrylics.

Load more