You can change both the line thickness and spacing of hatch lines.
The default value for hatch line thickness is 100%. Setting this value to 200% makes the lines twice as heavy; setting it to 50% makes the lines half as heavy.
The default value for the spacing between hatch lines is 100% (no change). Setting this value to 200% doubles the space between hatch lines; setting it to 50% cuts the space between hatch lines in half.