Coating leaves bumps on canvas....need help!

[iCanvas]

Ok, here is a pic of the bumps. Any advice will be helpful.

Thanks,

Gar

[Paul2660]

From that shot, they look like air bubbles, that did not pop. 

If the canvas is coated right after printing, the outgassing can cause air bubbles, but they tend to be much smaller. 

These would be possibly from a too heavy coating applied up too close to the canvas.  I would try thinning your mix and or spray, (add more thinner coats).

Paul

[Landscapes]

I've never seen this before.  I read your original post and see you are using Satin canvas.  These tend to already have a bit more of a bumpy texture I would say and are usually quite stiff.  I think these canvases also are sealed more which prevents out-gassing from behind the canvas.  In my opinion, if you're using a matte canvas, if any gasses do need to vent, they can always do so from the back.  I've never had a problem with out-gassing, perhaps Canon inks don't suffer from this as much.

The suspect might therefore be the coating, but its still interesting how in some part you don't get this and yet you do in other areas. 

Sorry I can't help but thanks for the pic.  Any chance you could provide a higher resolution and sharper image?  The reason I ask is because I assume an out-gassing bump would look a little bit like a volcano in that it would have a center depression, whereas if these bumps are random and closed, it might be possible to see if its just gunk buildup.

[iCanvas]

@landscapes: The bumps do not look like volcanos. The coating looks smooth when I apply it, but as it dried the bumps appeared.

I did an experiment this morning and my problem maybe that I am spraying too far away from the canvas. I think I need to be about 6" away from the canvas. There were no bumps when I did this. Hopefully that's the case. Thanks for everyone's input. I'll update this thread when I try my next coating.

Gar

[davidh202]

those don't look like air bubbles they look like lumps or  thicker possibly dried particles in the coating. When the  overall coating is still wet it is thick and the lumps are hidden. As the coating dries it shrinks  ( its carrier base evaporates), and the lumps do not so they stand out!!
are you straining the coating in a fine enough mesh before you load it in the spray gun, or possible moisture contamination in the air line ?

[nydigitalguy]

Coatings are essentially an acrylic (plastic) suspended in a carrier which dries rapidly when the coating is sprayed or rolled.
Always strain or filter your coatings prior to pouring the coating into the spray gun cup.  Use a 120 mesh disposable filter.  These filters can be purchased at any auto body supply store or at Harbor Freight in their paint department. (in store only, not available on the web) When rolling, I always filter the coating out of the gallon jug into a smaller cup.  I then pour the from that cup onto the canvas.  For best results, put on multiple thin coats.

The bumps on the canvas are most likely partially dissolved chunks of acrylic that have begun to solidify.  As you use more and more coating  from a gallon jug the air volume over the top of the coating increases and causes a skim coat to form on the coating if has been sitting around a while. 

Filtering the coating will also eliminate the dried crap that may flake off around the cap when you are pouring out of the bottle.  Shake or agitate the coating every once in a while and then let the air bubbles settle before you try to coat with it.  Another trick is to purchase an additional gallon of coating and pour some of the new coating into the old jug.  Then pour them back and forth from bottle to gallon bottle.  This mixing of old and new coating (provided they are the same brand and gloss level) will pretty much keep your coating stock fresh.
However, always filter the coating - new or old.