In gum bichromate printing we have been using Varn 14 Be lithographers gum solution, bought in 10 liter containers. From our supplier we heard that it is not available any more, and they sent what is supposed to be a substitutive product, “Agum O” solution by Hanns Eggen GmbH, Germany. The supplier assured us that it would be the same stuff, with same properties as Varn had.

But it isn’t! I made some tests with my standard pigment/gum/dichromate mix that I had used with Varn gum.

Some step table tests with “Agum O” gum and Schmincke and Linel pigments.

In my quick tests with step wedges I got very stained results. No matter how I mixed the sensitizer my pigments always stained the paper base heavily.

I tried to google for some information on “Agum O” but couldn’t find much. This gum feels a bit watery compared to Varn. Some sources refer to it as synthetic gum, and on this Finnish web page it is said to contain also dextrine in addition to gum arabic.

I couldn’t use this gum! So I decided to mix my own. I bought gum arabic as fine powder and mixed it with water at 1 + 2 (100g gum + 200ml water). The solution became somewhat thicker than the standard 14 Be gum, but some gum printers prefer it at this strenth.

I will need to recalibrate my gum printing workflow, so I guess it’ll take a while until I get some results posted here…