c# - RenderTarget2D not preserving transparent background -

i'm working on project. 2d using spritebatch.

i'm having things explosions use custom effects not apply rest of image. here flow far:

1)clear background

2)draw explosion sprites

3)capture image , implement effects separate rendertarget2d

4)draw background

5)draw rendertarget2d created in step 3

6) draw else

the problem i'm running rendertarget2d created not transparent in areas not drawn on. result, background drawn in step 4 not shown.

i have tried graphicsdevice.clear(color.transparent) following calls setrendertarget(null). however, still getting purple background.

any ideas?

i'd post code, there's have parse through.

if follow flow should work;

    graphicsdevice.setrendertarget(rendertarget);     graphicsdevice.clear(color.transparent);     // draw stuff texture     graphicsdevice.setrendertarget(null);      graphicsdevice.clear(backgroundcolor);  // important clear here     // draw background     // draw texture     // draw stuff