painting tubes

Hi all, I've been trying to up my acrylic game lately, and I'm just struggling. The biggest issue I'm getting is a "crackling" effect on the inside of the blank. I can't tell whether it's the blank itself, the adhesive, or the paint that's doing it, but I've gotten it on pens I've done with...

My first fountain pen. To make it my pen, the acrylic blank, as unique as any blank can be. I pained the inside of the tube with acrylic paint and a que tip. White at the tip, red in the middle and black at the cap end. Not really happy with the applications, went on thick and I had to sand...

I'm having an issue!!! I took some blanks and wanted to see how different they each looked, having a painted tube in different colors. I painted one half in white and one half in black. I painted both the tubes and the hole drilled through the blank, as I was told the glue will show if you only...