TOO MANY VARIABLES
1. the exp time of 2-3 hours is much to long as is the stated time for the tanning unit--the "cyanotype" material may be the problem-sounds like the senitised solution is deep in the support and/or not formulated properly-i allways start all my experiments with commercial "blueprint paper" material as it is so consistant and will get me into the ballpark fast
2. a single wt fiber base paper can easily be made transparent with "torch fuel"-this is liquid parafin that usually has citronella in it and has been descented --you could use regular kerosine but the fumes will be harsh--baby oil is ok but much too oily
3. resin ctd 'paper' is not paper-the reason for using it as a neg is that there is no fiber grain that will intrude into the print--HOW-EVER- the brighteners that are put into it flouresce very strongly under uv, and it may be that with such long exposures the very bright glow of the support(this would be visable under uv only ) is causing the 'bluring'
4. with so many variables it is very difficult to know what the actual problem is untill some kind of known constant is in the equation--blueprint paper and the tanning unit would be a easy way to test as both are constants
vaya con dios