Making all white in an image transparent

Here is a tip to make all white in an image transparent. This is really useful if you want to remove an intricate image off a white background

1. copy the image to a new layer and delete the background layer
2. copy the image to a new layer again and INVERT it
3. copy the inverted layer into the clipboard, and switch off its visibilty for now
4. go back the the +ve image and create a layer mask
5. press ALT whilst clicking on the mask thumbnail
6. paste the inverted image, then click back to the image thumbnail in the layer palette
7. duplicate this new layer until necessary (5 times?) and delete the inverted layer you created at the start
8. merge down the layers one by one (Ctrl-E) choosing to “apply mask” each time