What tenses to use in a paragraph?

I have several questions regarding tenses in paragraph form. If I start a paragraph in the past tense, coud I switch to present tense in the middle of the paragraph, especially if I am describing something.

For example, I’m talking about a particular process in the past tense, but when I’m describing what this process is, can I use the present tense or do I have to continue using the past tense?

Thank you,

It sounds possible, but the only real way to know whether or not it is correct in the context you have in mind is to see the paragraph.

Hi Huyn,

There is no need to worry about changing tenses as from past to present. Using the present tense in a narrative can be effective when you want to make the action sound actual - as if it is happening now.