First, a quick background. I am new to professional printing and photography. While not my main profession, I hope to build the skillset and portfolio to provide an alternative career path.
Last summer, I bought an Epson 7890 and a Canon ipf5100 and from day one, gloss differential and bronzing was an issue for me, particularly with the ipf5100. After some research, I concluded that a gloss coat would provide the desired solution. This led me to Jon Cone who gave some great advice. Using a 1430 as a test bed, I obtained the results I was looking for, save for one major problem: pizza wheels. Thus, I concluded a vacuum drive printer was required and purchased a meticulously maintained Epson 4880. I get stunning results.
While looking for the 4880, I sent a few prints to a leading Digital-C shop.
Comparing Epson 7890 color prints with a GO overcoat to Digital-C:
On glossy paper, the Epson prints with GO, the Epson prints have a greater dMax and more pleasing colors, particularly reds and skin tones. The Espon GO prints have the right amount of gloss, whereas the Digital-C are too glossy. While the Digital-Cs may be slightly sharper under a loupe, the overall impression is the compared to Epson 7890 gloss prints with GO, Digital-C prints look amateur, especially when hand holding. TBH, Fuji Crystal is a bit on the flimsy side.
On Luster paper, the results where closer, with the Epson 7890 GO covers prints again showing a better dMax.
GO also provides a bit of scratch protection.
On that note, the glossy Digital-C print came with some scratches from improper packing and shipping. Did I mention both "professional" prints were improperly cropped...
GO on matte prints also increases dMax and adds rub/scratch protection. However, Canon inks on glossy paper are incompatible with GO; however, Canon inks on matte paper is compatible.
All my prints now get a GO overcoat and the result is equal to or better than any other process.