A problem seen in your video is that the actual Gradient tool is not shown in your Tools panel. I am guessing your Tools panel has been customized, because the Gradient tool appears in the Tools panel in all of the default Photoshop workspaces. So the first thing you want to do is add the Gradient tool back to your Tools panel, and then you will be able to use it.  The gradient icon below your Tools panel is not the Gradient tool; as Bojan has noticed, that is the Gradients panel. The reason the Gradients panel doesn’t work on a mask is that as you have seen, it adds a Gradient preset in the form of a new gradient fill layer — the same as if you choose Layer > New Fill Layer > Gradient. However, the Gradient tool is able to create a gradient on a layer mask.

I am also looking for a solution that matches your description but the foreground to transparent gradient is not the solution I need. Say I have an image with a white background and a red shape. The red substance is translucent and uneven. Parts in some areas are thicker than others so you can see parts of the white background peaking through the red color but never all the way. This creates a gradient within the shape from red to white in several areas. What I want is to remove the white and just leave the red as a transparent png so it can be overlayed on other images or backgrounds. I am not finding much help since most tutorials are focusing on basic gradients and transparencies.

It's definitely a bit convoluted now, so unless I am not seeing an easier path, we have to, from left to right: ·   · Select the new gadient tool, and run a gradient across the image. · Double click the gradient in the layers panel, which opens the Gradient Fill panel. · Double click the gradient in the Gradient Fill panel, which 'finally' opens the Gradient editor. · I started with a simple foreground to background colour gradient, because I wanted as close to a clean state to start with. · To adjust opacity, you need to add a new swatch 'above' the gradient, which is the white square I have highlighted in yellow. · Note that the transparent area is most of the image in the above screen shot. To make the transparent strip more narrow, add another black swatch on the left, and red on the right. The colour swatches go below the gradient, but to adjust opacity, place swatches above the gradient. · OK, that's the new way, but you can do it a lot more easily with the Classic Gradient. · Select the gradient tool, and Classic gradient in the Options bar. · Use the gradients drop down, and select Foreground to Transparent. · Make a new layer · With your first colour selected, drag the gradient from one side of the layer to the other. · Note you can hold the Shift key to force the gradient to be horiziontal. · Now select the other colour and sweep a gradient the other way. · Foreground to Transparent allows you to continuously add to the layer, where as foreground to background overwrites the previous gradient. · For instance: · The new gradient tool is powerful, but definitely clunky.