How to make psmask tiling transparent to background topography

Hii experts, I am john. I am using gmt psmask in order to mask map areas with no data table coverage. However, I am successfully able to create tiling over the topography base map.Now my question is I need to make tiling transparent in order to see the background topography,for this i set -t50 in psmask but it doesnot work,still it gives opaque tiling on the background topography, even after converting ps to pdf. can anybody suggest a better solution for the same.Thanks.
my code is given below
gmt psmask xyz.dat -J -R -I5.0/5.0 -S10 -t50 -K -O -P >>
gmt surface xyz.dat -I0.5/0.5 -R -Gdata.grd
gmt grdsample tdata.grd -Gdata2.grd -I0.5/0.5 -V
gmt grdimage tdata2.grd -Cimgg.cpt -J -O -V -K >>
gmt psmask -C -K -t50 -O >>

telltale sign of a broken ghostscript I think. 9.50 works; 9.51-52 has broken transparency.

Hii sir thanks for your reply.However when i am using psxy and psbasemap transparency to background topography is visible(if i want to color a portion of area)…but while using psmask it doesnot work only flat opaque tiles are visible. Am i doing anything wrong by using -t50 or it would be something like -Gred@50.