Sunk/matte dark colour

Hi,
as I've been painting more very dark, almost black areas (sign of the times?), I've used ultramarine combined with burnt umber and tried to keep the layers fat over lean. I'm also careful to avoid white/light paint in the brush. Perhaps there´s been been a few days between layers, and what happens is that the pigment in the darkest areas sink into the previous layer and becomes very matte (lighter and less saturated). I've then oiled it out with an instant result, but when this oil dries a couple of days later, it quite often becomes matte all over again. I've noticed replacing umber with another color seemed to help, so perhaps it's has something to do with the umber.
Have you experienced this phenomena, and how do you avoid it?
For me it's been quite a struggle at times...
Thanks,
Erik 

Comments

  • dencaldencal -
    edited February 25
    PainterErik

    A surface with an oil sheen will always look glossy.
    As the oil polymerises it shrinks, hardens and exposes pigment particles that scatters the light. This gives the appearance of a dull surface. A particularly noticeable problem with the earth colours.

    The entire surface will assume a regular gloss level when varnished.

    Suggest oiling out for presentation or photography and a sticker on the back noting that this painting needs a final varnish on dd/mm/yy six months from completion.

    Denis

    PainterErik
  • It can be unsettling, but trust that the black will turn a beautiful satin/gloss finish when you varnish the painting in a few months.  Be sure to take before/after pics with your phone - it's cool to see it happen.    
    PainterErik
  • @PainterErik. It's the burnt umber. This happens to me all the time. But when you varnish the problem disappears. I like earth colours, especially the warm darkness of burnt umber but sometimes, when I don't want to be distracted by colour changes, I mix a colour from non-earth pigments that is indistinguishable from burnt umber.  :)
    KingstonFineArt
  • @PainterErik
    What Surface are you painting on? What paints and mediums are you using? Are you isolating brushes for different color/value ranges or taking brushes out of rotation if contaminated? All of these contribute the the almost inevitable sunken color. The only burnt umber I like is Geneva Burnt Umber.
    PainterErik
  • Thank you for all helpful advice! Did not consider the varnishing. Nowadays I paint on gesso-grounded MDF and use artist quality paint (Beckers). Might will avoid the burnt umber if I go really dark (near black) although I do like it. I overpaint when the surface is dry, say after 2-3 days, and ponder whether I should wait longer...
  • PainterErik

    A chalky gesso on top of MDF is a perfect thirsty sponge to suck down the oil from your paint, regardless of the paint quality. If the MDF wasn’t primed the dulling effect will be worse.

    Try an acrylic grounded aluminium composite panel and see if there is a difference.

    Avoid solvents if you can. Stand oil helps to retain a glossy surface.

    Denis
    PainterErik
  • Thanks Denis, good stuff. Anything particular you would use to prime an MDF? (I've a lot of them at this point and need to be able to use them). Could acrylic paint do the trick? 
  • dencaldencal -
    edited March 2
    PainterErik

    From https://www.artcons.udel.edu/mitra/Documents/MITRA_Rigid_Supports.pdf
    Fiberboard panels are created through a dry process that relies on chemical agents like urea-formaldehyde to bind the wood fibers together. High Density Fiberboard (HDF) is superior to Medium Density Fiberboard (MDF) as it has significantly higher internal bond strength and is less susceptible to moisture damage. However, HDF is still prone to planar deformation. Proper sealing or sizing and ground application can mitigate this problem.
    I wouldn’t use MDF because of the urea / formaldehyde and tendency to bow and twist in humid weather.

    Should you want to continue 




    My preference is the Dulux Precision because I paint on ACM and it is a metal primer 
    I get my supplier to tint to a mid grey or an iron oxide.

    An acrylic is usually a plastic coating, which may craze or delaminate, whereas a primer is designed to penetrate the surface and seal from support induced discolouration and from oil migrating downwards.

    All edges and surfaces of the MDF need to be primed to stop atmospheric moisture absorption.

    Denis

    PainterErik
  • edited March 3
    It looks like you've already got a bunch of really helpful answers. One thing I would like to add is that you mix a very pleasant black with Ultramarine blue + burnt siena... since both pigments are transparent it's an extraordinary black for glazing. Add indian yellow and you can mix the whole spectrum of colors with complete transparency.
  • Hi PainterErik – You got some good information in the previous replies. I will add to it (and perhaps the confusion) by saying that:

    1. Sinking in (dull, matte areas) can result from several different causes or combinations: substrate, substate sealer, ground, pigments naturally containing metallic dryer element (like burnt umbers’ iron oxide which you have already noticed), or added dryers, frequently found in alkyd media. Also, not enough oil in your medium, especially easy to do if you are putting in a lean wash as an underpainting.  I will hazard a guess and say I suspect your sinking in is caused by a combination of gesso ground, perhaps unsealed substrate, burnt umber, and painting lean.

    2. I find the MITRA site which dencal referenced a really good source of information. It is in English language, its free, and they have a great Resources section. Recently, someone asked the MITRA conservators a similar question: “DTM Bonding Primer by Sherwin Williams”: www.artcons.udel.edu/mitra/forums/question?QID=852

    I think several different commercial, non-fine art sealers/bonders will work well with HDF (or MDF). Depending on which country you reside, you will have different choices at different prices.

    I live in the USA and used XIM – UMA Urethane Modified Acrylic Primer-Sealer-Bonder to seal HDF panels on all 6 sides. After the XIM, on the painting side, I used an acrylic ground, sanded, and then applied a lead oil ground (do NOT sand – lead dust!) to get the velvety surface I like. It is relatively quick drying (lead) but not oil-sucking (oil ground last layer before painting). I never use gesso (too thirsty, too brittle). I don’t paint lean, but do paint thin. I do use lead and other natural metallic-based paints. Sometimes I use alkyds which contain a very little amount of dryer. Overall, I don’t have a sinking in problem – but never say never :) 

    I also paint on ACM and mostly on purpose-made Arches oil paper. I prep both to seal the substrate from the painting surface, and spend a lot of time prepping the surface. It seems to work.

    I am going to offer a different observation about varnishing: I have seen and heard stories about sinking in not being corrected visually by varnishing. I think it depends on the varnish; the low molecular weight ones like Regalrez (commercial product name GamVar) don’t do much for sinking in. I have no personal experience varnishing (but never say never).

    I think you got a lot of good information from all the DMP folks. I think you will probably have to experiment a little to find out the combination that works for you. Please post your results here so we can learn from your experience.


    Estee
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