I tried making coasters using opaque coloured base/tekta top layer and cut pieces of white opaque rod on top to add spots. However the white rod did not fully fuse at 810 which is the temperature I always use for full fuse. Please can you advise me what I should do to get the rod to fully fuse flat? Thank you.

Though officially 'T' Grade, this rod is now (since 2009) suitable for kilnforming, but can be prone to devitrification. Very viscous; will flow later and less than other glasses. Consider a design solution to avoid or remove potential devitrification: cap with clear or sandblast/remove devitrification through coldworking methods.

This colour is very stiff and not the best choice for this design i would recomend uing another white, such as warm white, cream or french vanilla.