Clean the damaged area of the vase with acetone and a soft cloth. Allow it to air-dry for a few minutes.
Set up your syringe kit materials, and cut the tip off of the adhesive-filled syringe. The syringe will have two small nozzles that contain two different adhesive agents you will mix together.
Lay the plastic blister on a flat surface, and then push the adhesives out of the syringe onto the blister. Make sure your amounts are equal.
Mix the two adhesives with a toothpick until well combined, then carefully paint the combination into the crack on the vase using the fine, thin paintbrush.
Quickly wipe off excess adhesive with the corner of a sponge, and then allow the repair to harden on its own. Do not touch the vase for a few days.