I am using GIMP in a very basic way, to clean up scans of sheet music, using the eraser and pencil tools almost exclusively. I used to be able to erase completely with one click or brush stroke; now it takes more than one action. The brush is set to hardness 1 and opacity 100. Can anyone advise me what to do: I seem to have changed something, but I have no idea what. Thanks!
Check your opacity(100%) and spacing(0) levels.
Thanks for your reply. The opacity is set to 100, and the spacing to 1, which is the minimum. What does the spacing do?
each brush stroke can be spaced by a certain amount set with that
setting. Instead of one smooth continuous stroke it would have gaps at a
set distance.
Perhaps a more detailed explanation of your situation when you say it
takes more that one action. Is what you are erasing faded a little? or a
clean but partial removal?
Also since these are scanned items adjusting the scan setting will
improve what you have to work with, and lessen what needs to be removed.
Are these scans grey scale? b&w Line art? or full color?
also is Dynamics set to off? Check force is not set to 0
The scans are grey scale. I no longer have the originals.
When I erase a black area, either by moving the brush or keeping it stationary, there remains a pale grey image. Brushing again removes that. That is a particular annoyance when, for example, erasing round the edge of a curved object; to do that twice is time-consuming.
Where do I find the Dynamics setting?
Goto section 2.4, that has an image or the eraser setting for GIMP 2.10,
It is in the eraser panel just
You may want to consider adjusting the contrast and brightness of the image to was out some of the background, may reduce the number spots to touch up.
I you can attach a sample image, i’d like to see what you are working with.
Also check the Force, especially if you are doing small strokes.
Otherwise please post a screenshot of your UI?
The dynamics are set to off.
The facility to vary contrast is indeed useful, if not vital, to the cleaning process. For example, many pieces of old music are quite yellow with age, which of course becomes grey in grey scale. Most of that can be eliminated with increased contrast. The attached page was probably the worst that I have had to deal with, with writing obscuring the original markings. That could only be dealt with painstakingly tackling each area at a time.
Is the Force setting part of Dynamics? Because they are set at off.
I don’t know what UI is.
Are all these scans jpgs? This makes it tougher to clean up.
I can see any issue with the image being the cause.
So it is time to redo the gimp config file. Rename the old file
look in your home directory for .config/GIMP/2.10 Inside this should be the configurations files, not sure where windows or mac keeps them these days. Rename the file, and start gimp. It should recreate the default settings. Then then try editing the file and see if erase works.
To do the job you want to do I would personally use a paintbrush or pencil set to white or whatever shade you want to replace the cleaned up area with. But the eraser should achieve the same effect unless something strange is set in the preferences.
Also, some of what you are trying to tidy up could be fixed using the thresholds tool in GIMP. Certainly the big grey patch could easily be fixed. Here is a sample of the threshold tool applied to a selection containing the grey patch.
UI + User Interface, i.e. in this case a screenshot of GIMP showing your erasor settings. 
Many thanks to all who responded, and for their various useful suggestions. I have just found the Force setting, and it was at only 50%; increasing it to 100% solved the problem.
1 Like
Glad you got it sorted!
increasing it to 100% solved the problem.
This isn’t normal, because the 50% default is enough. As you can see in the screenshot below,
using all defaults including Force=50%, each stroke of the eraser completely erases the white layer and the black layer shows trough.
So you have fixed the symptom but not the cause and it will come back.
I was erasing unwanted black marks. Black would be erased to pale grey, and then, in another stroke, the grey would be entirely removed. You have removed white in one stroke; can you do that with black also?
You have removed white in one stroke; can you do that with black also?
Yes. One stroke makes the layer totally transparent, whatever its color.