Since researchers have to establish that they have in fact undertaken the research, it's logical for them to use the past tense in reporting its methodology and results in a step-by-step chronological fashion. Previous researches cited when discussing the report should likewise be rendered in the past tense. Although consistency of tense will be virtue in such reporting, however, it need not be a straitjacket. This is particularly when reporting well-established research routines that are better described in the present tense--but, of course, rendered as reported speech as in this hypothetical example:
"We followed the following procedures prescribed by Smith et al in their landmark 1997 experiments:
"1. Immerse the material in a boric acid solution;
"2. Heat the solution to 85 degrees Centigrade;
"3. Titrate the heated solution to eliminate impurities that settled at the bottom..."
