If the glass looks feathered or fernlike then its probably glue chipped glass. Examples of glue chipped glass can be found on antique slot machines, stained glass designs, and other flat glass pieces.
The first thing you have to do is mix the glue and heat it. You can use most any glue, along as the glue doesn't have any additives in them for pliability. For every square foot of glass to be covered you need to use about 3 ounces of dry glue.
The second thing you have to do is mix two parts of tap water to one part of glue. You then need to let the glue soak for about an hour. After it has sat for about an hour you then need to cook it in a double boiler over low heat until the mixture is smooth with no bubbles. Make sure not to use direct heat, necause glue burns easily. While waiting for the glue to cook you can start working on the glass. Prepare the glass your working on by covering it with a resist tape. Cut out the area the area you want to chip, and then sandblast the exposed area. Most any grit size will do. After you have sandblasted the glass brush the surface clean. Now you can apply the glue.
Once the glue is dry and firm you are ready to go onto the third process. Place the glass piece in an oven at 125 degrees farenheit. After a few hours the glue will begin to pop off. When the glue pops of it takes layers of glass with it. After this is completed you must scrape off any residual glue.