Processes of making a non-woven glass fiber mat are described. The process may include forming an aqueous dispersion of fibers. The process may also include passing the dispersion through a mat forming screen to form a wet mat. The process may further include applying a carbohydrate binder composition to the wet mat to form a binder-containing wet mat. The binder compositions may include a carbohydrate, a nitrogen-containing compound, and a thickening agent. The binder compositions may have a Brookfield viscosity of 7 to 50 centipoise at 20° C. The thickening agents may include modified celluloses such as hydroxyethyl cellulose (HEC) and carboxymethyl cellulose (CMC), and polysaccharides such as xanthan gum, guar gum, and starches. The process may include curing the binder-containing wet mat to form the non-woven glass fiber mat.