Church tradition speaks of the purifying fire of Purgatory. This fire cannot possibly be a physical fire because the personal souls do not have bodies.
We have explained on first page that the body does not feel pain but the conscious soul does. So it would appear that this fire is spiritual, that it is an intense suffering of the soul like the suffering experienced by the soul when the human body is burning. This fire does not consume the soul like a fire does a human body. It is a fire which purifies the soul of venial sins, the punishment due to sin and any disordered inclinations of the soul. It is a temporal suffering which will diminish in due time revealing holiness and glory of God.
So, what is this fire? It consists of the soul encountering the holiness of God which is experienced as intense suffering due to its imperfections.
Proof that there is a period of purgation after death is the fact that we pray for their souls. If they are in heaven, they don't need our prayers; if in hell, no prayer will help them. We pray for the souls in purgatory because our prayers helps to shorten their sufferings on their way to the heavenly vision.
I offer You the most Precious Blood of Your Divine Son, Jesus,
in union with the Masses said throughout the world today,
for all the Holy Souls in Purgatory,
for all sinners everywhere,
for sinners in the universal Church,
those in my own home and within my family. Amen.