Sanding an oil painting questions

whunt

I have read posts that you can sand down parts of an oil painting that has dried in an effort to fix/change what you previously painted. 
Is there a particular grit of sandpaper that should be used? If you are sanding canvas, do you sand down to the white canvas?
What is the best way to clean the canvas after sanding before painting?
Thanks for any advice.
Bill 

tassieguy

I've sanded small areas that I wanted to change.  But only because the paint there was fairly thick and I didn't want raised edges from the old brushstrokes to show through the new work. If it had been smooth I would have just painted over it. Try not to sand the gesso/primer off or you will have to prime it again before you can paint on it.  I used a fairly fine sandpaper for that reason.  After sanding wipe the dust a way with a soft cotton rag. 

whunt

OK thanks, @tassieguy
It is a practice canvas (I guess they all are at this point ) that I put paint on too heavy with a knife. I want to sand it and give it another try! 
Hope you are on a quick road to feeling well. 

tassieguy

Thanks, @whunt. I'm on the mend. Slowly. 

Reusing canvases is a great way to save on materials. Once you paint over it no one will know it's a reused surface. And you just might knock out a masterpiece on it.  

broker12

I'm going to mention something I have already posted here . . . PAINT ON CARDBOARD.  I do this, but only if I'm relatively certain that what I'm doing is practice or a quick study.  Cardboard has several positive features . . . it's free and most of your local dumpsters are waiting to serve you;  It is already toned to about the right value to work on;  I seal my cardboard with clear acrylic matte medium.  You can cut it to sizes that suit your work.  I've painted lots of studies on this stuff, and saved a lot of money.  Just a thought for penny pinchers.

whunt

Thanks @broker12. Sounds like a great idea!

whunt

I need to start taking notes on so many of the very informative past posts, such a wealth of information. 

Abstraction

Gamblin technical support recommended to me 150 grit. It seems a bit rough but too fine and you can sand out the tooth. 

A_Time_To_Paint

So happy to see this post.  Have been considering sanding out part of a larger painting and didn't really know how to do it until now.

MichaelD

whunt said:

I need to start taking notes on so many of the very informative past posts, such a wealth of information. 

In case you didnt know if you click on the wee star to the right of the title of a post it will save it in your Bookmarks here on the site.

whunt

Thanks @MichaelD , a bit embarrassed that I didn't know that!
Thanks @Abstraction, I had some 180, it seemed to work ok, but I haven't painted over it yet to see the actual results.
@A_Time_To_Paint, my situation similar, a larger painting that a part when totally wrong, knew it wasn't right when doing it, but kept going anyway. I was thinking to just scrap it but I still want to try and save it, even if its only for the practice.

GTO

I have used 100 grit at first and then 200 or 300 grit sandpaper. I use the wet/dry type paper.  I sand the area when dry.  I only sand down to remove brush marks and raised paint levels.  I then wipe with isopropyl alcohol before painting over the area.

MichaelD

whunt said:

Thanks @MichaelD , a bit embarrassed that I didn't know that!

Hey no worries, there was a time when I didnt too 

whunt

Thanks @GTO - I was thinking that the area should be wiped with something moist to remove the fine dust that will inevitably be left after sanding. I was thinking maybe a towel moistened with Linseed Oil but isopropyl alcohol moisture would evaporate quickly which makes sense. 

dewald

@broker12 Just to be sure Im not lost in translation and/or a complete idiot. By cardbox do you mean the brown boxes items are packaged in e.g. a tv or microwave?

Romans611

Be care sanding paints ... especially lead and cadmium. Cadmium is 10x more dangerous to the body than lead. I believe it affects the body in a similar way as lead. The main way these heavy metals are ingested is through the mouth (eating or drinking while you paint) or inhalation (breathing dust if you sand it). I would not sand a painting that had lead or cadmium in the paints. By the way I am not sure how the other paints would affect your body and lungs if air born.

whunt

Thanks @Romans611. I wore an N95 mask and did it outside - hopefully that would help to alleviate the dangers. That said though, I do not think enough about the dangers involved with the materials we use. I have painted casually on/off for many years in oils but I am new to the forum and DMP (few months), and was a bit startled at seeing the health warnings posted on the videos!

Romans611

A N95 will help protect you, but fine particles will get through. You need a mask that has a solid seal around you nose and mouth. In the US it is called an APR (air purifying respirator). Do a internet search for "APR Half Mask" and you can see what they look like. I have sanded a canvas - it was to remove the brush strokes so I could re-use the canvas for another painting (save money). I used a MSA APR that was provided to me for work. Out side on a windy day will help also.

whunt

Thanks @Romans611, much appreciated. I will look into that. I have only sanded one painting for the same reason as you and only first heard of doing so on this forum. I have learned more about art in the last few months than ever before!

Forgiveness

Have you considered wet sanding? This keeps the dust down, wipe clean with a slightly damp soft cloth and let dry a few days, a week. You would still need to wear a mask tho.

Suez

I don’t know if it would work as well with paint but the old masters used a pumice stone for sanding layers of gesso. They used bread to remove the debris.

If you want to try it you can buy a nice fine grained rounded off pumice stone for a few bucks.They are sold, these days, for removing calluses from soles of feet.

The high-tech cleaning gel made for safely cleaning keyboards and car detailing might work well for removing sanding debris.

whunt

Thanks @Forgiveness and @Suez, as expected, more great and unique ideas from DMP! 

whunt

@GTO also suggested using wet/dry sand paper & cleaning with alcohol.
The old masters found ways to make things work using what was at hand, like pumice stone. It's hard to imagine the challenges they faced in those times without the technology and communication we take for granted today. 

Suez

@whunt, even with modern technology things can run amuck.

 NASA spent a fortune developing a pen which could reliably write in outer space. The Russians used pencils.   

Desertsky

@Whunt - if your painting has heavy metal pigments (lead, cadmium, mercury, etc.) in it, I would suggest not sanding it down. Even if you are protected by wearing a mask, you will still be releasing heavy metal particles into the environment.

I know that this will still be a very small amount compared to manufacturing industry, but still...

PS - my pedantic evil twin says that oil paintings on canvas have grounds, not (traditional) gesso.  She says other things as well, but I am taking her away for more mood-controlling medicine.

tassieguy

If the paint does have heavy metals like cadmium in it, then I agree with @Desertsky. I wouldn't sand it. I'd just paint over it if I wanted to use the canvas again. If there are any thick impasto ridges you want to get rid of first, you could slice these off with a palette knife, if they are still not completely cured. There will be no dust from doing this and so these large pieces shouldn't be dangerous providing you don't eat them and they are properly disposed of. And if all this is too difficult it might be simpler to use the other side of the canvas so that you can make a clean start with a nice new surface. If you do this you will need to make sure it's sized and primed first. Famous artists such as Van Gogh re-used canvases like this.