Glass fine particle deposit and method for manufacturing glass preform

A method for manufacturing a glass preform, the method comprising:

• manufacturing a transparent glass preform by heating, at a first temperature, a glass fine particle deposit in which a pH of glass fine particles on a surface of the glass fine particle deposit is 5.5 or more and less than 8.5;
• and
• measuring the glass fine particle surface of the deposit by a SCI (Specular Component Include) method using a spectrophotometer and determining whether a color difference ΔE*ab with respect to a white calibration plate is 5 or more,
• wherein in a case where the color difference ΔE*ab is determined to be 5 or more, the glass fine particle deposit is heated in an oxygen-containing atmosphere having an oxygen content of 10 vol % or more at a second temperature lower than the first temperature, and then the heating of the glass fine particle deposit at the first temperature is performed, and
• wherein in a case where the color difference ΔE*ab is determined to be less than 5, the heating of the glass fine particle deposit at the first temperature is performed without heating the glass fine particle deposit in the oxygen-containing atmosphere.