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Does pencil bleed through paint?

I got the impression (from both forum and general web searching) that there is no definitive answer to the question.  So I thought I'd just test it myself.

I scribbled lines on a lightly-stained wood panel, using both the SoHo recommended yellow pencil, and a No. 2 pencil, as shown on 2017-07-12:



Then I painted over these lines using Geneva Titanium White, having cleaned the brush between applying the two swatches.  This was also on 2017-07-12.



When I look at this on 2017-08-29, there is a distinct yellow tint to the No. 2 pencil (right hand side) swatch:



There are now dots on both samples, presumably dust in the air.

In general, it's not dots of pencil coloration, it's a general discoloration.  This sample has sat in an open windowsill for six weeks.

Can anyone tell me, or guess at, what happened?  Help me Obi Wan @dencal, you're my only hope.
BOB73Summer

Comments

  • I see that they have both changed color.  They both dried darker.  The one on the right is more aqua.  The one on the left is more pale blue.  Does this mean that if you want a beautiful aqua result you have to scribble a No. 2 pencil beforehand?  I'll wait for Denis's reply as well.  Interesting.  I thought painting was easy.
    PaulB
  • Well isn't carbon black a very dark blue? Is it possible it's mixed very slightly with the white?
    PaulB
  • Pencil will lift up when painted over. I've heard that it can take a while for this to happen too. I've personally experienced it and would encourage you not to do this. It makes the paint dark, muddy, or gray.
    PaulBForgivenessanwesha
  • I agree with Renoir, and I did witness MikeDerby experiencing pencil coming through not long ago in one of his portrait blogs. I found so much controversy on the net, but most frequent advice was to not use pencil to be safe. What Mark C. recommends is great and I found vine charcoal successful results when wiped away some, as it leaves stains the ground on the canvas, or can use spray fixative over it.
    PaulB
  • PaulB

    Here is an extract I posted before on this topic.

    BTW I read only yesterday that the migration of graphite is a myth.

    21) Graphite can migrate through the paint layers...

    This has become a common misconception amongst artists that can be easily explained. Most paints containing fatty acids (oils, alkyds, and egg tempera) can become more transparent as they age. The predominant effect is caused by the conversion of higher refractive index pigments (such as lead white, zinc white, etc.) into soaps, stearates, and other complexes that have a lower refractive index, and therefore create a more transparent paint layer that eventually exposes the underlying paint layers or underdrawing. In oil paintings, this is further compounded by a slight increase in refractive index that occurs in oil binders over time. This given the optical impression that an underdrawing (done in graphite, for example) is “migrating” to the surface when in fact it is simply a natural chemical change that has occurred in the overlying paint layers. This phenomenon is also associated with the term “pentimenti,” as the increased transparency of the uppermost paint layers can reveal earlier compositional changes and even unrelated paintings or sketches.

     

    https://www.artcons.udel.edu/mitra/Documents/MITRA_Myths_FAQs_Misconceptions.pdf
    Some comments;

    • A control swatch, white paint with no underlying pencil would have helped understand the color shift.
    • The application of pencil in this test is very heavy, fine to push for a result, but it's not typical pencilling.
    • Pencil is not carbon black (Richard_P) but a combination of graphite and clay.
    • It is not possible to be definitive about subtle color shifts among the vagaries of digital photo compromises, lighting, JPEG compression, monitor calibration, resolution etc. We must rely on your visual observation.
    • Was the time of day, lighting, shutter speed and fstop controlled for the before and after shots?
    • The texture of the brush stokes in the before and after shots indicate a very different light direction.   
    With these issues in mind I am surprised how blue the Titanium white appears.
    After six weeks of drying there does indeed seem to be an attributable color shift due to the lead pencil.

    Compare two swatches; My caveats above apply here too.



    These are sampled from the top quadrants of PaulB's before (wet) and after (dry) images for TW over graphite. Apart from the texture they appear similar in value. The difference in value is attributable to the light direction difference.

    We have had numerous demonstrations from Mark about how color perception is influenced by adjacent color. In this case I think our vision is saturated by the orange staining and we perceive an echo in the white that is a combo of yellow and blue, hence a greenish hue.

    Why doesn't the first swatch show this shift? Don't have the energy to go there :#

    Denis

    PaulBKaustav
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