I just started using spray contact cement. What should the correct spray coverage look like?
From contributor J:
I use StarStuk spray contact cement. It sprays like silly string with bubbles, but in a wide angle pattern. I make two passes to get near complete coverage. I've never seen anyone else spray this stuff, so I can only guess what I'm getting is the way it's supposed to be. I don't get the complete thick coverage like you get when you roll it or brush it on. We've used it for a couple of years with no delamination problems, so even if the texture and pattern are wrong, it's working just fine.
P.S. I always do 2, except a tad differently. First coat as full as possible on entire surface, second primarily total perimeter 6" wide, since edges fail long before centers. I also will do a light second on middle, but not a concentrated shot.
The trick to the stuff, I've noticed, is:
*Don't pile it on, especially with veneers, as it will show through as a lump.
*Allow it plenty of time to dry. I've let it sit for over an hour before sticking them together (was an accident) and they held great.
*Proper coverage and spray pattern are a bit subjective, but if it's globbing up, you are too heavy.
*Keep the spray tip cleaned with lacquer thinner on a rag.
*Use a good hand roller to press the parts together if you don't have a press or a pinch-roller.
In my opinion, a pressure fed Binks 2001 gun with a contact cement tip and air nozzle along with Binks fluid-all hoses and a 2.5 gal pressure pot is the perfect setup. You are looking at around 300 for the gun, 100 for the hoses, and 100 for the pot. (Get a Craftsman pot - it works just as well.) You will also need a filter that will prevent moisture getting into the pot from the airline. I use the type that houses a paper roll. (I cheat and use toilet rolls.)
This is a reliable setup that will spray the same every time. This is important so that you can adjust it and your technique to get the best result as you gain experience and learn while using the setup. This sounds silly to say, but you will be surprised how often I had to wrestle with lesser setups just to get them to work and almost every time, the lesser setup produced different results. After much frustration and asking many questions here, I finally got it right. With the Binks gun and hoses, I can take it out, hook it up and it will work. Yes, the gun costs more than most, but just the time saved alone has paid for this setup.
Very important! Use good contact cement. Always go for veneer grade contact cement even if you are working with micas. I just find that good contact cement sprays better.
As for the pattern... I set the gun to spray a round shape. I never allow the gun to make strings, because they tend to telegraph. I look for a fine splatter that hits the veneer while it is still wet, then I simply wiggle the gun back and forth to cover the area as one would coloring with a crayon. I use 10 psi pressure on my pot, 60 psi at the gun and I usually close the fluid off at the gun and then open it until it stops spitting and produces a nice even splatter/spray. I adjust the spray pattern as follows. If the full fan pattern is 10 and the round pattern is 0, I put the pattern adjustment at around 3. This gives you good coverage and enough air to transfer the CC and help dry it once it hits the veneer. I make a few tests on some scrap before I get down to it. When you are done, check your air cap and clean it with a rag and some solvent. When you work with veneer, it helps to use 2 ply veneer.
Comment from contributor K:
Contact cement is sold with the least amount of proper use of the product. The most important factors are applied grams per meter, 100% coverage and bond time for the conditions you are working in.
The gun you use is the difference between lumps and complete coverage. Air pressure is extremely important with 50PSI I can apply contact cement like paint with 1 mill dry film at 100% coverage per side. I work with aircraft mfg and complete converage is very critical for reducing movement for heat and cold temp ranges. It can be done but you must use the proper products to achieve fantastic results.