The problem is caused by applying a zig-zag pattern of this fast MMA-adhesive on only one substrate.
By applying the adhesive on both substrates, spreading it out completely over the surface, these air bubbles could be prevented.
Three of the samples show air bubbles and a zig-zag patern.
The samples in this picture were made by participants of the European Adhesive Bonder training course during their practical exam. The three samples on the right show air bubbles and a zig-zag pattern. Measurements on peel resistance would show such irregular results, not representative for the adhesive bond, nor the adhesive. The sample on the left shows a much better results, which was achieved by different way of applying the adhesive.