I have notice a few post about adding Magnesium Carbonate to ink for letterpress. I am wondering if anyone has feed back about when to add, how much to add and any draw backs. We are using soy based inks. Since the Soy based inks are somewhat loose we are also wondering about adding a tack increaser to build the ink body. We are not having a big issues we just want to be the best we can and fine tune our image. What got this post started was the great way our metallics lay down and we want the standard inks to play just just as nice. We will listen to any ideas.
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The first thing I would do is talk to your ink maker. I’m sure they are making your ink to a specific tack value, and they can change it if you request them to do so. If you are buying a very small amount of ink, and buying it ready-made, the ink maker is still the best person to recommend a specific additive to change the tack.
By talking to them, you may find that your ink maker sells a different ink formulation which has a higher tack, which you could try.
From the view of an artist who tries not to have too many inks on hand but uses them for a variety of purposes, I would say mag carb works best when added slowly. Think of it like kneading flour into dough. I usually take an inky knife, dip it into the mag and then use what sticks to the knife and start mixing. Too much mag too fast results in waste. Obviously the amount of mag depends on how much ink you are mixing up. Very small jobs are hard to stiffen up properly because of the minuscule amount of ink required for the job.
To Geoffrey’s point, if you are only using it for letterpress, I would recommend either switching inks or providers to find something more to your liking.
We actually found an interesting way around the issue. Since we have found colors with a high transparent white build always seem to print dark, especially with a solid, we added a special blend of dense opaque white our ink maker had built for letterpress use. We had made it to print white ink and it worked great at the time. It is a pigment enriched hugh tack very dense ink ( like chalk) white opaque ink. I added to the pre mix PMS and to look at the blend on the table I thought no way this would work but it hit the color dead on with a big solid and the density of the white improved the lay down.