What is the test for bias against a judge in a civil case?

Appellants first assert they did not have a fair trial. They say the statement of the trial judge quoted in the margin which was made after he had stated what the findings and judgment were to be 'expressed his state of mind throughout the trial and impaired his impartiality and swayed his judgment.' ¹ We find no basis for the assertion. 'It is well [168 Cal.App.2d 330] settled in this state that the expressions of opinion uttered by a judge, in what he conceives to be a discharge of his official duties, are not evidence of bias or prejudice.' Kreling v. Superior Court, 25 Cal.2d 305, 310-311, 153 P.2d 734, 737. Conviction in the mind of a judge, based on his observation of the witnesses and the hearing of their testimony, does not amount to prejudice against a litigant.