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Tag Archives: acrylic painting

In: Paints

Acrylic vs. Oil: Conservation Properties

Many artists dream about having their work exhibited in museums that would preserve art for generations. Even if your painting is not going to get there the question about the archival properties of your work is still important. Some art can show signs of deterioration, such as:

1. Fading or discoloration. Over time, exposure to light and environmental factors can cause colours to fade or change. This is particularly noticeable in artworks created with pigments with poor lightfastness.

2. Cracking or flaking. Paintings, especially those done on canvas, may develop cracks or flakes due to aging, changes in humidity, or improper handling/storage. This can result in the loss of paint layers or sections of the artwork.

3. Yellowing or darkening of varnish. Varnish applied to protect and enhance the appearance of a painting can yellow or darken over time, altering the original colours and clarity of the artwork.

4. Mold or mildew growth.

5. Loss of adhesion. In some cases, the layers of paint or other materials may detach or lose adhesion to the support, leading to flaking or detachment of sections of the artwork.

Let’s take a look at these aspects of oil and acrylic paintings.

Fading or discolouration

In oil, it can come from two aspects: wrong pigment use or wrong conditions of paint application. If we compare oil to acrylic, pigment use will be about the same. As both refer to opaque mediums, pigments are supposed to have similar lightfastness at use. However, oil drying processes are much more complex and longer than for acrylics, so fading can occur if drying is happening at lower temperatures and unstable or high humidity. 

For acrylics, during the water evaporation process, discolouration may be noticeable much faster. It’s not an actual colour loss, but rather the effect of wet colour vs. dry colour (similar to a wet and dry rock). Also, generally speaking, professional oil paints have a higher pigment load in the tube than acrylics and fewer fillers and thickeners that help keep colour almost unchanged from application to the end of the visible drying process (provided that storage conditions are met). Excessive fillers may make paints “milky” and less vibrant after full drying, especially in acrylics.

Cracking or flaking

Oil paints, generally speaking, potentially develop more cracking than acrylics. Especially, if an artist didn’t follow the “fat over lean” rule. Fat over lean refers to the principle in oil painting of applying paint with a higher oil-to-pigment ratio (‘fat’) over paint with a lower oil-to-pigment ratio (‘lean’) to ensure that the film is flexible and durable. 

The Canadian Conservation Institute (CCI) points out that oil paintings are particularly vulnerable to low relative humidity (RH) conditions, which are very common indoors during Canadian winters. 

In low RH conditions, the size, ground and paint layers become more brittle and higher stress within the layers can develop. Below 35% RH, they are more likely to develop cracks, which in turn can lead to lifting paint and paint loss. Also, RH fluctuation of more than 10% can contribute to cracking, especially for impasto paintings. In other words, storage conditions are very important to prolong an oil painting’s life.

What about acrylic paint, there is currently extensive research being undertaken to increase our understanding of the composition and properties of modern paints. Even though acrylic paints form a more flexible film than oil paints and seem less prone to cracking, we don’t have statistical data enough to determine if similar defects develop with natural aging. 

What we know is that acrylic paint becomes more vulnerable to cracking at moderately low temperatures. It increases dramatically in stiffness at temperatures of +5 …10 °C, which is not too low considering Canadian winters. The potential for cracking at these temperatures makes handling and transporting paintings questionable in Canadian winter conditions. 

Yellowing or darkening of varnish

Usually, this is attributed to oil paintings, especially quite old ones. To protect the painting surface, we use damar varnish that tends to yellow and darken with time as it absorbs dust and some humidity from the environment. The good news is that it’s fixable. There are tons of successful restoration works performed over time when the old varnish was cleaned or/and re-applied. Painting layers themselves were not affected.

Even though acrylic varnish doesn’t yellow with time, it doesn’t provide proper protection for the artwork. According to CCI, acrylic paints tend to attract and absorb dirt at ambient or high temperatures making it impossible to clean the surface of acrylic painting without affecting and damaging the paying layer. Because of these, the CCI suggests protecting acrylic paintings with glass. 

Mold or mildew growth

High humidity or improper storage conditions can lead to the growth of mould or mildew on artworks, particularly on wood or canvas materials. Both acrylic and oil paintings may be affected by this equally.

Loss of adhesion

Here, we should go deep inside the polymerization process. In chemistry, monomers are molecules that can react with each other to form a larger polymer chain or three-dimensional network. This process is called polymerization and it goes differently for acrylic and oils.

Oil creates a durable bond with most of the surfaces, including metals, forming a flexible film. If the surface is porous, the bond will be even stronger. Acrylic polymerization takes place within itself and the only thing that holds the paint is its penetration to a porous surface normally provided by acrylic primer. That explains why acrylic paints are so easy to peel off from your plastic, glass, or even wooden palette. And, of course, the same thing may happen to your painting.

In: Manufacturing

Acrylic vs. Oil: VOC

In this series of articles, I’d like to look at these two mediums from a professional and responsible artist’s point of view, thinking about the artwork itself and the impacts that working with these mediums includes. There is no straightforward answer to what’s better and I don’t think such a question can be valid; this article is aimed to make an informed choice for this or that art project. I’ll try to be as straight to the point as possible.

What is VOC? 

Volatile organic compounds (VOC) means any compound of carbon (excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates and ammonium carbonate) that participates in air. Some VOCs have a distinct smell, while others may remain unnoticeable. Exposure to VOCs in indoor air may affect your health, depending on which VOCs are present, the level of VOCs present, and how long you are exposed. 

Some examples of VOC include formaldehyde, benzene, ethylene glycol, d-Limonene, toluene, acetone, ethanol, 2-propanol (isopropyl alcohol), methylene chloride, tetrachloroethylene and many others.

The World Health Organization (WHO) recommends a guideline value of 0.3 mg/m³ for total VOCs in indoor air.

Both oil and acrylic paints (we’re talking about artist paints, not industrial) emit VOC, but in different quantities and in different ways. You can find the information about VOC in the Material Safety Data Sheets (MSDSs) that most manufacturers provide. 

MSDS for the same product vary depending on country regulations and usually split based on pigment groups:

  • containing cadmium and cobalt
  • containing zinc oxide
  • and all the rest
  • These extracts refer to “all the rest” based on regulations in the same country and state (county).

Before we refer to the facts, let me ask you a question, Which paint would you choose, the first or the second?

“SECTION 7: Handling and storage  

7.1. Precautions for safe handling Precautions for safe handling: Ensure good ventilation of the workstation. Wear personal protective equipment. 

Hygiene measures: Do not eat, drink or smoke when using this product. Always wash your hands after handling the product.  

7.2. Conditions for safe storage, including any incompatibilities Storage conditions: Store in a well-ventilated place. Keep cool.”

“SECTION 7: HANDLING AND STORAGE 

Precautions for Safe Handling: Read and observe all precautions on the product label. Wash hands after use. Immerse contaminated rags in water. 

Cautions for Safe Storage: Store away from high temperatures, sparks, or open flame”

I’m not sure what would you prefer, but I’m voting for the second. The first one describes acrylic paints, and the second one refers to oil paints (I’m not disclosing brands here). 

Even very high VOC in paints doesn’t qualify to be labelled “toxic” as VOC compounds do not stay in your body for long being broken down and released with urine. However, prolonged exposure to VOC vapors can cause a variety of health effects, such as:

  • eye, nose, and throat irritation;
  • headaches, migraines and loss of coordination;
  • nausea and damage to the liver, kidneys, or central nervous system.

VOC in Oil Paints

In general, the VOC of artist oil paints (not industrial ones that you buy in construction stores) is less than 2 g/l. Meaning, for example, if you’re painting in lean technique and use 10 ml of paint, which is about a tablespoon size, your paint will emit about 20 mg of VOC and to maintain healthy standards 66.7 m3 of room space is needed. If your ceiling height is 2.5 m, a painting room should be 26.6 m2 or larger to maintain healthy balance.

If you’re painting in impasto technique, you’ll need a room about 10x larger. 

However, oil paint releases VOC slowly, while paints dry, meaning that the concentration of VOC will be lower than those estimates.

To keep oil painting safe, just don’t use or add turpentine oil or solvents. They have almost 100% VOC, reaching up to 1200g/l. Use linseed or other drying oil, solvent-free mediums, cleaners and varnishes. Keep your painting on the safe side.

Cheap oil paints may have solvent inside and emit more VOC.

VOC in Acrylic Paints

Generally, the VOC of artist’s acrylic paints is about 50g/l. For a lean technique, let’s use the same 10ml of paint. They will contain 500 mg of VOC and with the WHO’s norm of VOC level 0.3 mg/m3 we’ll need 1666.7 m3 of space, which is about 667 m2. If you paint in the impasto technique, multiply this number by 10.

The good news is that all VOC is emitted during drying time, which is quite fast and after the painting is cured, the VOC level is 0. In other words, in 1-2 days air quality with proper ventilation and filtration goes back to normal.

To compare, acrylic paints that contain mica powder (in other words, all metallic paints) have a VOC of about 300 g/l, and acrylic varnishes have 100 g/l. I saw artist’s acrylic products with VOC 500 and higher. Some acrylic gels and pastes may have very low VOC as no pigment or excessive water was added.

Acrylic dispersion/emulsion itself has a very low VOC. Making acrylic paints by yourself and using them right away is another solution to avoid intoxication. What is inside acrylic paints and why, you can read in the previous article.

In: Manufacturing

Acrylic vs. Oil: What Is Inside The Paints

In this series of articles, I’d like to look at these two mediums from a professional and responsible artist’s point of view, thinking about the artwork itself and the impacts that working with these mediums includes. There is no straightforward answer to what’s better and I don’t think such a question can be valid; this article is aimed to make an informed choice for this or that art project. I’ll try to be as straight to the point as possible.

Oil Paints

Historically, oil paints are made from pigment and oil. However, fresh-made paints, especially if they contain mineral pigments, will start separating within a very visible time frame (some paints show separation even after a week from the manufacturing date). Copper Oxide pigments separate in 5-7 days, and earthy pigments, depending on their particle size, within 1-3 months. Organic pigments, due to their lightweight nature, may not show any significant separation even after a year of manufacturing. Pigment use is a separate topic, so I’m not going to pull it here.

As it can take 5 or even more years between manufacturing time and actual purchase and consumption time, manufacturers need to make sure that their paints are still presentable. So, to stabilize paints (depending on pigments) they use wax pastes as well as barium sulfate. To increase the quality of the painting and the elasticity of the film, some resins can be added. Usually, it’s turpentine gum (don’t mix it up with turpentine oil), dammar, mastic etc. To shorten drying time a small amount of turpentine oil may be added.

Some paints, depending on pigments and grade (studio, artist, pro) may have fillers that usually have a mineral nature: kaolin, marble dust, calcite, barite, talc, etc.

Professional paints have pigment, oil, wax, resins and a minimal amount of fillers.

Acrylic paints

Here, everything is much more complicated. Long story short, here is a list of ingredients:

  1. Pigment. The same as for oil. The different pigments used for acrylic and oil will be covered in a separate article. 
  2. Binder. It’s either acrylic dispersion or emulsion or both. They contain styrene and/or an alkyl methacrylate. The alkyl methacrylates used are methyl methacrylate, isodecyl methacrylate or stearyl methacrylate. Many terms, but all these can be simplified as monomers that form polymers after the carrier (water) evaporates.
  3. pH adjuster and dispersant. When we paint in acrylic, we expect that paint will be easily spread, and mixed with other colours. That’s why ammonia is an essential acrylic paint component. Pigments, as we know, are solid particles and tend to settle down on the bottom of the pain container with time. Ammonia helps to disperse the pigments evenly throughout the paint, thereby providing nice consistency and colour uniformity.
  4. Surfactant. These chemicals prevent paints from early cracking and provide an even drying process. Here we have ammonia again, glycerine, and propylene glycol.
  5. Fungicide. As acrylic has water inside and some organic and inorganic ingredients, paints need to have preservatives that stop mould growth. Here, it can be ammonia, formaldehyde, or petroleum by-products.
  6. Paints, that contain mica powder as well as very thick paints may contain solvent to prevent separation and prevent paints from drying in tubes.

Ingredients used in paints deal with safety and health issues. 

In: History

Acrylic vs. Oil: Brief History And Goals

In this series of articles, I’d like to look at these two mediums from a professional and responsible artist’s point of view, thinking about the artwork itself and the impacts that working with these mediums includes. There is no straightforward answer to what’s better and I don’t think such a question can really be valid; this article is aimed to make an informed choice for this or that art project. I’ll try to be as straight to the point as possible.

Oil Paints

It’s hard to say when the oil painting was really invented, as more and more evidence comes up with archeological searches (it’s saying that the first oil paintings found belong to the 7th AD), but we can definitely say that oil painting practice was actively adopted and developing during the Renaissance time, in 1500s. There were two main schools, based in the Netherlands (that led to the establishment of the Old Holland company) and based in Italy. Key contributors include Van Eyck, Giovanni Bellini, Leonardo, Titian, Vermeer and others.

The goal of oil painting was to create art that would last long and offer the optical sensation of depth, light and life. Initially, oil paints were made of pigment and oil. Some artists were adding resins made from saps of different plants and trees to achieve this or that optical effect.

However, later, when manufacturers started producing paints in mass quantities, oil paints got a broader use, including industrial and household paint. To shorten drying times, as well as to increase spreading properties, toxic solvents (such as turpentine and white spirits) were added.

Acrylic Paints

Acrylic paints were invented quite recently, in 1934, by the German chemical company BASF, patented by Rohm and Haas. The goal of the creation of acrylic paint was to replace oil paint in household and industrial painting with faster drying and less toxic solutions. They really did this job well and keep doing so. Painting walls with acrylic is much cheaper, less toxic and much faster than with oil.

By the 1960s artists adopted acrylic paints as a practice. All we know is that this time is associated with the mass-production and consumerism era.

In: Paints

Acrylic Paints for Decorative Arts

For craft purposes, such as decorating wooden boxes or painting on leather or fabric, acrylic paints work best. They mix well, can be applied easily, dry fast, form permanent film, and the cleaning is quite simple. Although all acrylic paints have pigments (or dyes) as a colour agent and acrylic dispersion (or emulsion) as a binder, they are not the same for different purposes.

Acrylic paints for fabric contain a special plasticizer, so after use and stretch your painting will stay. Paints are usually thinner and go inside the treads, that’s why absorbing cotton is one of the best materials to use for textile painting. 

Paints for silk are even thinner and look more like ink rather than regular acrylic paints as silk is very fine and colours should penetrate inside and between the treads so no film is left on the surface.

For leather, acrylic paints for fabric work very well, but they may not have enough adhesion. Even though we remove all grease from the leather top surface, perfect cleaning is not really possible, and paints may peel off the surface. So, special paints are recommended.

Hot techniques in glass and ceramics provide the best effect as they kind of fuse to the surface and form a semi-permanent connection between the materials. For cold techniques, acrylic paints can be applied. And here regular acrylic paints do not work well. Glass is very sleek and regular binder doesn’t stick to its surface very well. That’s why special acrylic paints for glass and ceramics have a special bonding agent to provide extra adhesion. Glass paints can be transparent or opaque, creating beautiful stained glass effects.

Another special kind of paint is metallic-looking paint. Don’t fool yourself, gold paints have no gold, just mica powder to achieve a sparkling look. Mica particles just reflect the light and, being coloured, they imitate different kinds of metal: gold, silver, copper, bronze or even some exotic colours. However, they will look metallic just in certain light. Also, paints with mica powder usually contain solvents and stabilizing agents for smoother application and to prevent the separation of mica particles. For a true gilding experience, use our gilding kit. It doesn’t have gold or silver either but creates a solid metallic look regardless of the games of light.

How to prime your canvas
In: Practice

How to choose right canvas: Part III, Sizing and Priming

How to choose the right canvas and why they are different – are most common questions in any art shop. We’ve already talked about stretching options as well as choice of fabric for your canvas. This time we’ll discuss the final step before your art appears on canvas – sizing and priming.

Canvas, when it’s raw, is just piece of fabric, meaning it absorbs moist and dyes before, during and after painting process. These mean if you paint on untreated canvas:

  • paint colours will look much different from what you have on your palette while you’re mixing colours
  • your painting will change with time and keep changing in unpredictable way

Also, as bare fabric is soft, makes folds and wrinkles fast that means any paint that forms a film (such as acrylic or oil) after drying may crack and fall off. 

That’s why sizing and priming are very important. 

Sizing For Canvas 

Before any primer or paint layer applied on canvas the fabric has to be sized. Sometimes we can skip priming, but sizing is a must. Why?

Canvas is a piece of fabric, which has threads weaved along and across each other. All this weaving process leaves micro-holes between the treads, creating air circulation and exposing your painting to humidity and other weathering from inside. Also, unsized canvas works like a strainer allowing micro leakage of the paint through it. Sizing is aimed to seal the gaps between treads and create one solid base for your painting.

Size is technically glue that covers all holes and gaps. Historically, artists were using glue made from natural materials. The most popular one was rabbit hide glue as well as bone glue that provides jello-kind substance and dries forming smooth and relatively stable film. 

Normally, artists were applying one layer with high-concentrated glue that looks like jelly and then, after full curing, they applied another 2 or 3 coats of glue that was much thinner and smoother.

I have to say, this kind of glue smells terribly and needs immediate application before it gets bad. RUSART Naturals offers sizing for canvas in 2 steps based on this old recipes. We added some essential oils into it to prevent from mold growing and eliminate bad smell.

Later, artists began using gelatine instead of bone or skin glue that offers similar properties. 

Nowadays, most manufacturers use synthetic sizing for canvas, such as Poly Vinyl Acetate or acrylic resin. As primer usually is also acrylic based, usually cheap canvas doesn’t have any sizing and has only primer, which makes canvas not suitable for oil painting and barely stable for acrylic painting. 

When buying a canvas, just look through it against the light: if you see light coming through gaps between the treads, stay away from this canvas (unless you want just to play around and show it away after short use). Good canvas always blocks the light well.

Primer For Canvas

Priming is important in making decision how to choose a right canvas. It’s technically the first layer that provides adhesion with canvas. Bad adhesion leads to peeling of painting layers and early damage.

However, priming is not always necessary. For example, a lot impressionists such as Claude Monet and many others worked on sized canvas without any primer applies and such technique also provides some interesting effects.  

Primer can have different kids of base: oil or emulsion. 

Oil-based primer consists of linseed oil mixed with chalk and white pigment. Historically, this kind of primer was used for oil painting as it provided a better adhesion between oil painting and canvas.

Before oil painting was developed in 16th century, artists used primers based on egg-yolk, casein (milk), rabbit skin glue or other kids of stable glues. This primer was mostly used for wood.

Then, artists were mixing oil and glue-based primers and created emulsion primers. Chalk and white pigment serve as hard particles suspending in flexible oil-water emulsion. Such primers reduce risks of cracking and shrinking.

There are many kinds of emulsion-based primers, including casein, polyvinyl acetate, acrylic and others. Well-primed canvas normally has 3 layers of primer before art work begins. 

Another thing that is very important to know when choosing a canvas is how much chalk was used in your primer. If for acrylic or tempera painting this factor doesn’t play the main role, for oil painting it’s crucial. Chalk is a very porous material and absorbs a lot of binder. This may cause a lot of problems for oil painters:

  • Uneven drying
  • Fading of colours
  • Cracking of painting layer

Only trusted canvas should be used for most important artworks.

(c) RUSART

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