Defining the Difference Between a “Crack” and a “Craze”


Figure 1: Varying the thickness of GOLDEN Crackle Paste results in a wide range of cracked patterns.


The Material Specialists here at Golden Artist Colors are often requested by artists to diagnose the reasoning for problems occurring in their paintings based solely upon their words used to guide us. One of the most common emails or calls require the understanding of whether the artist is discussing a crack versus a craze in the paint film, and exactly what shape the crack or craze is. Both of these conditions are caused by a similar mechanism of reducing stress in the paint layer. Often these stresses are built up during the drying process yet some cracks may only appear with some other mechanical and / or environmental stress in the future. Understanding the causes of these fractures in the paint film will both allow for corrective action or point the artist in a way to take advantage of what might be to others, a paint defect.


Figure 2: Close-up of a craze, formed in a thickly applied pour of GOLDEN Self-Leveling Clear Gel.

What the Heck is a “Craze”?

A craze is typically considered a surface defect, developing most often in acrylic paints or mediums that when applied, begin to form a skin while the material underneath is still fluid and wet. The very flexible acrylic film can usually stretch quite easily as the edges of the skin begin to dry, requiring the center of the film to continue to stretch as water evaporates and the film shrinks. In some cases, the center areas of the drying film can no longer take the stress of shrinking and a tear in the upper part of the film occurs. This then leads to a phenomenon where water and other volatiles are more able to be released from this area of the tear. It’s sort of like lifting the cover off a boiling pot to one side; all of the evaporative pressure is now targeted at this area of the film. Sometimes this tear can reach all the way down to the paint layers below, but even more often the surface film repairs itself, yet left with the scar of the original tear and still noticeable on the surface. Although a craze is a physical surface depression, it does not pose any long-term stability issues to the painting. The film formation process has not been compromised.

At times the crazing phenomena can occur in very thin films. More often than not, this sort of crazed surface is the result of the lack of a coating being able to wet out the layer below. So as the stresses caused by the evaporation of water continue, areas where the cohesive force of the acrylic film is greater than it’s attraction to the substrate or paint layer below, you begin to see these same crevices in the film. In extreme circumstances this crazing can actually leave breaks in the film.

Products which do not relax or flow after being applied to a surface do not have the same issue of crazing when applied. For example, Soft Gel, Heavy Body Acrylics, and Molding Paste are artist materials that are highly unlikely to craze even when applied generously to a canvas. The shrinking product’s structure remains stable during drying. One can overcome this by adding a generous amount of water to these products. The additional water simply increases the amount of shrinking that will occur in the drying process and therefore increase the stresses in the film.


Figure 3: Detail of a cracked painting section of GOLDEN Crackle Paste.

When is the Defect Defined as a “Crack”?

Cracks are also the material’s way to relieve stress. They can be identified by their crisp breaks. The sharp-edged individual pieces are defined as “platelets”. Some cracks occur when a hard, rigid paint layer is flexed further than it is physically capable of bending. These cracks run deeply throughout the entire painting. When decades-old oil paintings on linen are carelessly removed from their stretchers and rolled up tightly they are probably going to crack severely. Even acrylic paints, primers and gel mediums can crack. Acrylics are thermoplastic and when they are in cold climates they become increasingly stiffer. When they are rolled or unrolled in the wrong temperature they can crack, even if they exhibit no issues in warmer room temperatures.

Another reason paint layers may crack is because the underlying materials are swelling up, pushing against the less elastic layer. At some point the stiffer paint has to give, and it creates a cracked surface. Exterior grade housepaints are formulated with a high degree of elasticity in order to reduce the cracking that occurs when the underlying wood swells from moisture.

Some artist materials crack due to their formulation. When a product is overloaded with “solids” such as marble dust, it becomes more than the binder system can handle. The shrinking film tries to stay intact, but must yield at some point, and again, cracks are a result. This cracking resulting from a material being under-bound is observed in nature when a riverbed or lakebed dries up. The mud cracks, forming deep fissures. This phenomenon is the reason our Crackle Paste works. It relies on being under-bound just enough to develop a cracked (also known as crackle) layer. Of course, we have to be very careful as to modify the solids to binder level just enough to cause the pattern to develop, and still be stable enough for use within artwork. Proper surface preparation and sealing the surface after the cracks are done developing are paramount to long term stability.

In the Ceramics Industry crazes and crackles are both defects and decorative. They often are the result of the glaze recipe or the speed of the cooling off cycle after firing the pottery. The pattern develops as a means to reduce stress or tension within the coating. Craquelure is used to define a large or complete area of fine line patterns.

Unintentional cracking or crazing often happen during the painting process when the artist least expects it. Some are the result of applying a paint, gel or medium a bit too generously, and others happen because external factors such as temperature, humidity and air flow are not taken into account. Even if an artist has used a product successfully for years, defects can occur. When troubleshooting, consider the impact of the immediate environment and changes in the weather. What worked perfect in the summer may not work at all during the winter months.

Crazes can be minimized through careful planning and control of the product application and studio environment. While it’s near impossible to completely eliminate crazes from developing, one can greatly reduce their occurrence by:
• Working in a room temperature environment with little air movement, especially during the initial drying phase.
• Applying products thinly and avoiding thick puddles or dammed sections.
• Working on a flat, level surface.
• Avoiding movement of the work until it has cured, ideally leaving it alone for 3 or more days.
• Allowing underlying paints and primers to fully cure.
• Sealing the absorbency of the surface before applying a poured layer.
• Suspending a lightweight board such as Gatorfoam® just above the surface of the freshly applied medium to create a terrarium-like environment that slows the drying time down.

Take note of when crazes or cracks develop in your own work. Look at all of the factors present and narrow down the most likely factors that resulted in the defects and conduct tests to see if you can mitigate their development. The product you applied may be the wrong product for your desired application. If you are not able to figure out what’s going on, contact us so we can help you identify the problem.



12 Responses to Defining the Difference Between a “Crack” and a “Craze”

  1. Cynthia Ryan June 13, 2017 at 9:30 pm #

    Hi, My acrylic dirty pours are crazing. I want to add GAC 800 to my paint mixes.
    How much GAC 800 do I add? Do I add it to every colour or only 1 or 2 colours?

    • Michael Townsend June 14, 2017 at 11:54 am #

      Hello Cynthia,
      Thank you for your questions. The GAC 800 needs to be the primary product in all of the paint mixtures. I often mix around 10 parts GAC 800 to 1 part paint. This can be adjusted if you want more opacity or transparency, but more paint begins to result in more crazing, and can be color dependant. A 4:1 GAC 800 to paint ratio seems to be a good threshold for the amount of paint to add, but if you tilt the painting while wet and stretch the paint out it will dry faster and be a thinner paint layer, both of which help reduce the chance of craze development. You might also want to “tent” the fresh pour using cardboard or plastic to slow the drying time down. For small thin paintings you can simply use a clean pizza box.
      – Mike

  2. Carolann Blanco June 22, 2017 at 4:15 pm #

    Dear Cynthia,
    This was very helpful. I am very new to this, I usd to paint but after a couple strokes I can no longer express myself as I used to….but still have a lot of paints so pouring on a small scale seems doable to me…..but as I look at videos and Facebook, it appears cracking is a bad thing, yet some of my favorite pieces are ones with cracking….often used as examples of what not to do……is that just personal preference? Or is there something I am not understanding. I like texture or the look of texture but that seems to be something to avoid. Thanks for any insight!

  3. Karron Troil July 24, 2017 at 9:25 am #

    Hi Michael, if you get a large crack on an acrylic pour can it be filled in and with what Golden product? I used a mixture of GAC 800 and Liquitex Pouring Medium and a small amount of Floetrol. My painting looks great in all areas but one. Thanks, Karron

    • Michael Townsend August 3, 2017 at 5:37 pm #

      Hello Karron.

      Filling in cracks/crazes can be tricky to not make it stand out even more. I believe the best approach is to use the exact same mixture and skim it over like one does spackling. Remember that acrylics shrink, so several passes (allowing drying in between layers) should eventually result in a more uniform surface.
      – Mike

  4. Bethany Williams January 20, 2018 at 10:41 am #

    Thank you so much! Great article! Sharing to all artists I know.

    • Michael Townsend January 22, 2018 at 8:17 am #

      Thank you, Bethany!
      Your comments are much appreciated.
      – Mike Townsend

  5. Wally Bistrich January 24, 2018 at 4:37 am #

    Hi Mike,
    also temperature shocks might cause crazing:
    two years ago on a very hot summer day I applied a layer of self leveling gel. Knowing the studio would get even warmer when the sun turns around the corner I tried to slow the drying process (and thus to prevent crazing) by putting this small painting into the most shadowy corner of the studio, not being aware that the difference in temperatures in an old building can be enormous. I could immediately watch the fast crazing process. Fortunately spread almost evenly over the surface I could encorporate the crazes later.

    • Michael Townsend February 8, 2018 at 6:37 pm #

      Hi Wally.
      Thank you for your insight about factors that contribute towards crazing. Ideally acrylics are allowed to dry in “room temperature” which is within the 60-80 degrees Fahrenheit range.
      – Mike Townsend

  6. Denise September 17, 2018 at 5:15 pm #

    Mike, I’m just getting into painting with acrylics. I caught where you suggested a 60-80 degree when allowing paintings to dry. What do you suggest the humidity should be ?

    • Michael Townsend September 20, 2018 at 4:48 pm #

      Hi Denise.
      Thanks for your question.
      Temperature while acrylics are curing is important because it can impact the coalescing of the acrylic polymers. Too cold, or too hot, can alter the process and create weaker paint films.
      While painting, higher humidity helps provide longer working time. For fast drying, lower humidity accelerates this. So, for most acrylic artists they prefer having more painting time and when they are done painting and need the paint to dry quickly it is very helpful to have low humidity and some air movement. But humidity doesn’t greatly impact the curing of the paint as temperature does. As with “room temperature” maintaining a comfortable humidity level is the studio is preferred. Anything lower than 70% RH will help the paint cure. Higher than 70% will help slow the drying time down. When doing pours, high humidity can greatly reduce the chance of crazes developing.
      – Mike Townsend

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