When I plan out my spells, I take into account several factors. The primary factor is of course the moon and its phases.
I also consider the Qabalistic correspondences for each Sephira or Qlipha, but for casual spells with demons I look into the Goetia to determine the nature of the demon. There are a couple of pages in Goetia and there you will find information about metals for seals.
Then I know for example that the seals of Haures and Bune have to be made from copper. Copper is the metal matched to Netzach.
Having this information is enough, because then we will know that Haures and Bune are summoned during Fridays, and their paper seals can be green, etc.
We will also be wise if we summon these two demons during the astrological hour of Venus. But that is not enough, because the moon may be off its path in the sky.
There are 14 mansions (areas in the sky map) and the moon travels through these 14 mansions during its 28 day cycle.
When the moon travels from one mansion into the next, it can be off its path just for a certain period of time. This period can be as short as one hour and as long as several hours.
If we do our spells during these “unbeneficial” hours when the moon is in a negative mode of movement, we may obtain zero results or the spells may backfire on us. The results of such spells may look like a cosmic joke.
To be on the safe side I always consult the Lunarium. You will have to change the settings of the Lunarium to obtain the exact intervall of the moon’s “void period” displayed for your city.
I hope that this information was helpful.