'Bootstrap Glyphicon, How to change weight?

I don't see any change with any of the values I can specify in the CSS property font-weight. Do you know how to solve?

Thanks in advance

.glyphicon-custom {
  font-weight: lighter;
}
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<!-- Latest compiled and minified CSS -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">

<!-- Optional theme -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap-theme.min.css" integrity="sha384-rHyoN1iRsVXV4nD0JutlnGaslCJuC7uwjduW9SVrLvRYooPp2bWYgmgJQIXwl/Sp" crossorigin="anonymous">

<!-- Latest compiled and minified JavaScript -->
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>

<div class="form-group has-feedback"><input type="search" class="form-control"/><span class="glyphicon glyphicon-search form-control-feedback glyphicon-custom"></span></div>


Solution 1:[1]

.someSvg path {
    stroke: white;
    stroke-width: 3px;
}
    <div style="width: 100px; height:100px;">
      <svg viewBox="-10 -10 120 120" class="someSvg>
        <path d="M 50,0 L 60,10 L 20,50 L 60,90 L 50,100 L 0,50 Z" class="arrow" transform="translate(85,100) rotate(180)"></path>
      </svg>
    </div>

Sources

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Source: Stack Overflow

Solution Source
Solution 1