Gel Inks

Viscosity

Gel inks are fluids with a peculiar rheology so that they can work also at a very low viscosity. For this reason if the tip is not sealed all the ink will flow back from the refills; the silicon follower in fact acts only has a non-drying agent and has no resistance on the ink flow.

Another issue linked to their rheology is the “push back effect. In this case the cap is producing an air tight force against the wall of the tube and pushes the air through the tip causing irregular writing. Due to this pressure the ink englobes the air which blocks the flow. Very important is to design the cap so that the tip enters into the rubber stopper before clicking into the body. In this case the air exits from the cap and is not pushed into the tip.

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Ink Follower

Please use following ratio in order to obtain the best possible performances:

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       Tube Ø                 Follower QTY

        (mm)                          (mg)

        3,550                          130

        4,000                          180  

        4,500                          260

        5,000                          350

 

Centrifugation

It is necessary to remove the little air bubbles englobed into the ink during the manufacturing and, to push the silicon paste, injected on the back of the refill, directly against the gel ink in order to avoid its evaporation. Due to the different types of inks, the centrifuging needs to be carried out with the maximum care.

 

Dye base 

Dye based gel inks can be centrifuged without any problem for a long period of time and at high speed, provided that the seal between the adapter and the tube, point and adapter and, point and plug are suitable to block ink leaking under pressure (in the tube by the centrifugal force).

 

Pigment base

Gel inks are made with non-soluble pigments well dispersed in the ink, but with a specific gravity higher than the base in which they are dispersed, therefore, under the action of a centrifugal force they have the tendency to separate forming a solid layer on the tips; this will block the ink feeding causing inconsistency in writing. Therefore it is very important not to exceed the threshold of the centrifugal force which will cause the separation of the pigment. The suggested centrifugation speeds are depending from Centrifuge diameter and are the following:

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Centrifuge Ø        Rotation Speed       Time

   (meters)                    (rpm)               (min)

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       0,50                        900                    2

       0.60                        800                    2

       1.00                        600                    2  

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Glitter, Pastel and Metallic Inks 

The difference of specific gravity between the pigment and the ink base is higher that the standard pigmented inks, therefore more unstable. Consequently, the speeds and times  of centrifugation have to be reduced and the second centrifugation after 48 hours it absolutely necessary for getting a good de-aeration

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Centrifuge Ø        Rotation Speed        Time

   (meters)                    (rpm)                (min)

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       0,50                        500                     1

       0.60                        450                     1

       1.00                        350                     1  

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In order to achieve the best possible performance, after first centrifugation, refills should be left tip down following one of these methods:

 

a) for at least 48 hours at a temperature of about 45°C (recommended for refills with the protection wax drop on tip).                                                                                                  

b) for at least 72 hours at a temperature of 30-40°C (recommended for refills with tip protection different than above).

Allow refills to cool at room temperature then carry out a second centrifugation at a temperature not  higher than 40°C and not lower at 20°C.

 

At last we suggest to store refills horizontally and avoid temperatures above 40°C.