Why is it important to understand how Crackle Products work?


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 weathered door, Bergamo, Italy (get image from Howard)

Crackle products have long been used to replicate the failure of paint and plasters as they weather and age. This is a critical consideration, as the coatings formulator is faced with the task of developing a product that “fails” in a very specific and controllable manner, but still provides a robust and durable surface. What this means for the decorative painter is that cracking products require more attention to detail as they are not as inherently foolproof as other decorative paints and textures. In the case of crackles, the product must be designed such that it does not completely coalesce as the water and solvents evaporate from the wet film, so that it will fracture (crack) as the film shrinks as it dries. But we also want the crackle to adhere tightly to the substrate as it fractures. As a result, as the curing film shrinks and cracks, it puts a lot of stress on the layers of paint and other products underneath it. If there is a layer with weak adhesion, as the cracking texture moves and cracks as it dries it can cause that layer to separate from what is beneath it and there will be a loss of adhesion. The pages on Crackle surface preparation and protection detail some of issues that painters need to be aware of as they design finishes that incorporate these products.

Include Amanda's story here with pictures of saran wrap, paint and cardboard...step by steps... This example illustrates the forces involved with a crackle application. The material with the greatest strength will draw the weaker in whatever direction it wants to go in as it dries. This is why the strength of a painted layer can surpass the strengthe of the substrate. The greatest bonding strength will win over the weaker.

Step 1. We loosely taped a piece of saran wrap to a piece of cardboard. This illustrates a coat of primer (saran wrap) to a wall (cardboard). Any dust that lies between the layer of paint and a wall or paint and plaster will act like rollers or create glide undetectable to the naked eye. Step 2. We rolled on a layer of paint to the saran wrap. The paint simulates the crackle materials coating the previous painted layer (saran wrap). Paint contracts as it dries and creates air pockets and cracks.

To create a "reveal", borrowing from the paint conservation world, simply use a sharp x-acto knife or blade to scrape back thru the existing paint layers. If at any point you find a layer of chalky surface, this means the wall has been "skimmed" with joint compound or patching plaster and using the Crackle materials should be reconsidered. (Include step by step pictures.)

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