Conservation Damage Terms
Paint Cracks or Craquelure (French for crackle)
Craquelure – Also known as Age Crackle or Cracking Paint, are fine to very wide and noticeable crack patterns throughout a painting’s surface, caused by shrinkage of paint, or drying of oil in the paint medium.
Draw Crackle – Generally a series of parallel cracks emanating from the corners of a painting creating a ripple effect. These are caused by either keying out the painting so far that the paint cracks, or from the painting being very slack on its strainer or stretcher.
Pinwheel or Sigmoid Crackle – These spiraling cracks (seen between the bottom of the figure’s hair and top of her dress) are from something hitting, or being leaned against the canvas of a painting from either the front or back sides. These cracks frequently don’t show up for a long period of time after the incident occurs.
Stretcher Bar Crease – These are cracks that are parallel to the outside edges of the painting, or along the length of a vertical or horizontal interior stretcher bar. They are formed when the canvas in slack on its’ stretcher or strainer, and the paint cracks along the inner edges of the four outside stretcher bars, or along the interior bars.
Traction Crackle - This term is used when an upper layer of paint or varnish dries to the point that it cracks and shrinks into noticeable paint or varnish islands, but the layer below doesn’t, so that the lower layer is now revealed. This is usually very visually disturbing.
Paint Problems – (In increasing order of severity 1-7)
1. Blanching – When a layer of varnish or paint turns white and semi-opaque. This is generally caused by this layer developing very minute cracking. Light no longer easily penetrates through this layer, and bounces in all directions. This makes the layer look white, just like a frosted piece of glass. If you put water on the frosted side, you can see through it again as if it were a clear piece of glass.
2. Cleaving Paint or Cleavage – This is when the paint layer has cracked, and is now separating from its canvas, panel, or wall support.
3. Interlaminate Cleavage – Separating paint between layers (support to ground, ground to paint, or wall to paint).
4. Quilting - This is a term that has more to do with the back of the canvas than the front. The paint has cracked, and is cupping, but is still attached. These cupped areas of paint have now caused the back of the canvas to resemble quilted fabric.
5. Tented Paint – After the paint initially cracks, and starts to detach by lifting a little around the edges. Two of these paint areas lifting adjacent to one another form what looks like a tent. This stage of paint damage is just before Cupping Paint and then Flaking or loss of paint.
6. Cupping Paint - After paint cracks and is actively detaching itself from its substrate, it then begins to curl like a potato chip. At this point, the paint’s edges are exposed, which are sharp to the touch.
7. Flaking Paint – Following the cupping stage, the paint chip completely lets go from its substrate and falls off, creating a loss of paint.
Paper Conservation Damage
Acid-Burn or Acid-Matt Burn – A dark red brown staining just inside the edge of a window mat on your artifact. This is caused by moisture activating acidic particles in the adjacent acidic matboard. It is surprisingly not on the part of the artifact below (in contact with) the mat because this portion of the artifact and mat were not directly exposed to higher humidity levels. Acid-burn on a paper artifact can also be created by the flow of air through the crack of two wooden backing boards.
Acid-Free - This descriptor refers to paper-based materials, which have a pH of 7 or above, where 7 is neutral, below 7 is acidic, and above 7 is basic. Paper made from cotton or linen is acid-free. If you take your paper artifact to be matted, you ideally want to ask for mat board that is “Museum/Conservation grade, and made from cotton or linen rags.
Cockling – Undulations in the paper artifacts normally flat surface. This is not wrinkles, but gentle waves in the paper where it is not lying flat. This happens frequently if your paper artifact has gotten wet and dries, or if it has been exposed to levels of high humidity.
Foxing – Small red/brown blotchy looking spots on a paper-based artifact or document. These look like rust spots, but are actually an impurity in the paper that are acidic, and have discolored due to exposure to high humidity levels, or contact with other acidic materials. The spots can also be caused by fungal growth.
Inherent Vice – Built-in internal stress or incompatibility of materials within an object.