Arm bone moving piece of torso without weight paint


So I’m fairly new to blender and made a character with armature. I tried the automatic weight painting and I tried to weight paint myself, with the same result: While moving the arm bones (legs and rest of the body are fine) (both arms have this problem) in pose mode or weight painting mode a piece of the torso moves with it. In weight painting it is just blue indicating it shouldn’t move.

to better understand my problem I added a video below:

Thanks in advance,



Its hard to see in weight paint mode, but part of the torso is still weighted to the arm bones.
Also, because the torso is not weighted to any other bones (im guessing), the influence to the arm bone acts as weight 1.0.

The reason you find it hard to remove the weight in weight paint mode, is probably the brush Blend mode and other settings.

One way to remove the weight from the torso, is to use the vertex groups panel.
Select the mesh then switch to edit mode. Deselect all vertices.
Go to the Properties > Mesh Data > Vertex Groups panel.

Select the vertex group with the same name as the arm bone ‘upper_arm_R’.
Then press (Select) in the vertex groups panel.
This should select all the vertices which are weighted to the vertex group.

Deselect all the arm vertices where you want to keep the weights.
So only the problem areas should be selected (some of the torso vertices).
Press remove to remove weight from the selected vertices.

The torso could be weighted to other arm bones aswell, like the lower arm or the hand.