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koolkatz
07-10-2009, 05:26 PM
Greetings to all,
I am new to WC so I hope I am posting this in the right spot!
Anybody know what causes shiny or dull spots in large areas of one color?
Also, is there anything to be done when one has put linseed oil over a painting--long story,won't do again!--and it stays tacky and never dries.

Thank you in advance,
Abby

CareyG
07-10-2009, 06:30 PM
Hi Abby, welcome to WetCanvas. :)

Shiny and dull patches are common in oil paint. They relate to the oil content of the paint and absorption. When, for instance, a lower layer (or your painting ground) has "sucked" the oil out of an upper layer, then you get a dull area. If there is a larger amount of oil in a layer, then it will be more glossy. This is also sometimes due just to the properties of the pigment (how much oil it will contain, etc...many dark pigments, for instance, will dry dull).

Normally, it is not something to be worried about, and usually you can use retouch varnish to even out the sheen in the short term, and a final varnish will take care of it after the painting is sufficiently dried (six months to a year).

As for your other difficulty, you can try to remove the oil with solvent, but I suspect that it is better to just chalk your experience up to...experience. :) I suggest using a minimal amount of medium (or perhaps none) until you get a better handle on how oil paint itself behaves and you better understand the *whys* of using various mediums.

Hope that helps!

~!Carey

koolkatz
07-10-2009, 06:40 PM
Hi Carey,

thanks for the info!

Best regards,

Abby:)

CareyG
07-10-2009, 06:43 PM
You're welcome! :)

~!Carey

jdadson
07-10-2009, 07:01 PM
As Carey says, some oil paints just naturally dry to a matte finish. But one thing that you need to watch out for is going back with the brush into paint that you've already applied. Put it on and leave it be. Once paint has gotten scuffed up, no amount of oiling out or varnishing will make it right.

It is okay to oil out the surface, but apparently you used too much oil. Rub it in very, very thinly. Fingers work well for that.

koolkatz
07-10-2009, 10:28 PM
Hi JD,
Thanks for the advice!
Abby

TheBaron
07-11-2009, 08:30 AM
Greetings to all,
I am new to WC so I hope I am posting this in the right spot!
Anybody know what causes shiny or dull spots in large areas of one color?
Also, is there anything to be done when one has put linseed oil over a painting--long story,won't do again!--and it stays tacky and never dries.

Thank you in advance,
Abby

Normally this can be associated with adding too much turps in a mix with the medium or painting with just oils and medium,then washing a brush out in turps and using that same brush to blend two colours together which evidently will leave a matt appearence.

PattyC
10-29-2010, 02:54 PM
As Carey says, some oil paints just naturally dry to a matte finish.

Is there a list anywhere of which colors are more prone to drying to a matte finish than others?

I am finished with my first layer of a painting I am so happy with, except for this. I do suspect that I am guilty of not being consisten with how much medium I use, but also suspicious that in my grisaille underpainting I used Mars Black and that that is the culprit. I am so disappointed about this and just praying that varnishing in the end will help. But I'd like to learn more about this problem is possible.

Thanks and I hope nobody minds that I have revived this discussion.

Lucy

sidbledsoe
10-29-2010, 03:05 PM
Lucy, varnishing will fix it and even out the surface sheen. I don't know of a list and even then different formulations of the same colors may vary. Adding oil medium will alter the oil percentage, painting on less absorbent grounds will cut down on sinking in. Leaner, less oil rich colors are more prone to sinking in and fatter, more oily ones dry glossier. Umbers are notorious sinkers. However, I know of one artist that prepares his canvas with more gesso followed by an oil based ground, then uses a glazing medium for layers and gets no sinking in at all with burnt umber, one of the most notorious sinkers.
I like the holistic approach about thinking of, and then mitigating surface sheen that Gamblin addresses in this page (http://www.gamblincolors.com/newsletters/pdf/GamblinStudioNotes17_SurfaceQuality.pdf).

PattyC
10-30-2010, 08:36 PM
Actually that article from Gamblin helps a lot. Thanks Sid. They have a great web site I think. I refer to it a lot. Hadn't read that one.

Lucy

Ribera
10-30-2010, 09:26 PM
All paint's sold at standardized consistencies, more pigment,
less oil the better; you can add more oil (or solvent) at your
pleasure.
- Solvent and oil being less expensive.
At the commencement of a multilayered image, obviously
one desires the paint lean; one may even add solvent.
At the conclusion, w/glazes, fatter.
Invariably, as one lays the paint on, some areas of the sur-
face absorb too much oil, and you get faded, or sunken-in
areas - other areas fine.
Of course, in the process of crafting the image, one can't
wait till the final varnish, 6 months to a year later, to
know if it'll be right. One must either oil-out or retouch var-
nish it to bring the hues to fullness; at that point one's rela-
ting tones over the whole image.
Having parts correct and parts wrong won't do.
Retouch varnish is simply a more dilute final varnish - more
solvent, less resin; it can be painted right atop the sunken
areas - In fact, it's designed to be.
Oiling out is merely adding a little oil specifically to the areas
that lack it, dull.
If an area's dull, it simply lacks oil - add more (or resin).
r

fxoflight
11-30-2011, 01:15 PM
Hi folks-

Normally I paint on masonite hardboard panel primed with 2 or 3 layers of acrylic gesso, or on acrylic primed canvas. I've never had an issue with dull patches until now, when I tried painting on oak plywood primed with 4 to 5 layers of acrylic gesso. As far as I can remember I obeyed the fat over lean rule, when applying my second layer. It looked fine, until a week later when dark patches started to appear in my portrait painting, ruining the look.

This is completely disheartening, but I hope I can safely say the problem is with the oak plywood and insufficient surface preparation. Does this sound like the issue? Are masonite panels less absorbant than oak plywood? As I said I've never had an issue with dull patches until the oak plywood, so I can only assume this is the problem area.

Thanks in advance.
-fxoflight

Mares Rex
11-30-2011, 04:01 PM
Have you sized the plywood properly?

Scorpio
11-30-2011, 04:15 PM
Here is a FAQ from Winsor Newton. Several of the topics address this subject.

http://www.winsornewton.com/main.aspx?pageID=394#o5

In my experience, it is the earth colors that sink the most.

fxoflight
11-30-2011, 04:30 PM
No, I don't think I've sized the plywood properly. Acrylic gesso on plywood does not seem to be enough to create a good ground, in my case.

Since I haven't experienced this issue with masonite hardboard panel (primed with acrylic gesso only), am I safe to assume that masonite is actually a better support for oil painting? I don't want the ground I'm painting on to change the look of the finished painting in a year's time, for example. That would be so disappointing.