OpenGL fade out/in not working
===

I'm trying to fade in/out an image using JOGL. I can render the image fine, however it doesn't fade in. Below is the code:

    private void render(GLAutoDrawable glad) {
    GL2 gl = glad.getGL().getGL2();
    
    // Prepares the rendering, things such as disabling depth, clearing the buffer bit etc
    setUpGL(gl);

    BufferedImage background = main.getCurrentState().getImage();
    // Render the background, adapted from here: http://bit.ly/QjeusP
    renderImage(gl, background, background.getWidth(), background.getHeight());

    gl.glEnable(GL2.GL_BLEND);
    gl.glBlendFunc(GL2.GL_SRC_ALPHA, GL2.GL_ONE_MINUS_SRC_ALPHA);
    gl.glColor4f(0, 0, 0, alpha);
    gl.glBegin(GL2.GL_QUADS);
    gl.glVertex2f(0, background.getHeight());
    gl.glVertex2f(background.getWidth(), background.getHeight());
    gl.glVertex2f(background.getWidth(), 0);
    gl.glVertex2f(0, 0);
    gl.glEnd();
    gl.glDisable(GL2.GL_BLEND);
    }

the variable alpha is a float, which is incremented by 0.1 for each render, if it exceeds 1.0, it is decremented by 0.1 until it is less than 0, then incremented, and so on.

Any help would be greatly appreciated.
Thanks, Mike