After using Texture2D.SetPixel and Apply, can't reset texture using SetTexture

First I am storing a texture in a global variable, in Start():

private Texture2D tex1;
tex1 = (Texture2D)GameObject.Find("plane1").GetComponent<Renderer>().material.GetTexture("_MainTex");

Then I execute some code like this to apply a border to the texture, when a key is pressed:

var borderColor = new Color(1, 0, 0, 1);
for (int x = 0; x < image.width; x++) {
for (int y = 0; y < image.height; y++) {
if (x < borderWidth || x > image.width - 1 - borderWidth) image.SetPixel(x, y, borderColor);
else if (y < borderWidth || y > image.height - 1 - borderWidth) image.SetPixel(x, y, borderColor);
}
}
image.Apply();

That code works.

Then later, upon a different keypress, I try to load the original texture back again with:

GameObject.Find("plane1").GetComponent<Renderer>().material.SetTexture("_MainTex", tex1);

This doesn't work.

Please help if you have some clue why. I've been googling, trying things, rinsing-and-repeating for hours now. Going a litle crazy.

 

Please use code tags when posting code so it's easier to read: https://forum.unity.com/threads/using-code-tags-properly.143875/

Where does your image variable come from? Could it be that it points to the same texture as tex1, so your border code is changing your original texture and not a copy of it?