The natural conjunctiva method, this method is also basically suitable for inks that are mainly dried by oxidative conjunctiva. The principle is that under certain temperature and humidity conditions, the minimum time required to make the ink surface of a certain thickness into a solid film is the natural conjunctival drying time of the ink.
The natural conjunctiva method can also be measured using instruments. What we introduce here is a relatively common method in our country.
(1) Equipment and materials
①Apparatus.
( i) Knife.
( ii) Minor Ink Knife.
(iii) scraping (ink) knife.
(iv) Glass plate.
(v) Pins.
② material. 150g writing paper.
(2) method
Take a piece of writing paper similar in size to the scraping paper, and use a small punch to carve a 2 x 3 cm square hole into it. Then place it on a glass plate.
Use a small ink knife to take an appropriate amount of oil to be tested and place it on the edge above the paper hole, and then use a scraper to scrape the ink through the square hole and fill the square hole with ink.
After removing the writing paper, a ink layer that is the same size as the square hole and has a certain thickness (its thickness is approximately equal to the thickness of the paper) is left on the glass plate at the original square hole place.
Estimate the time, and regularly use the tip of the pin to stir the ink surface to see if the ink surface layer becomes a solid film.
Calculate the time required for the ink surface to become a solid film after the ink is scraped into a thin layer on the glass plate , which is the natural drying time of the oil under test.
(3) Precautions
① When scraping the ink through the square hole of the paper with a squeegee, the force should be appropriate, not too large or too small, so as not to cause inconsistent thickness.
②Observe very carefully when touching the surface layer of the ink with the tip of a pin, because it is more difficult to judge when the skin begins to form. After using a pin to move a place, it cannot be moved in the same place next time.
③Modern quick-drying inks contain more oil-oil. During the drying process, they will escape through the surface of the ink, which may bring difficulties to the judgment and should be paid attention to.
④ The measurement of natural conjunctival drying should be carried out under constant temperature and humidity conditions from beginning to end. The temperature is 25±1°C. The relative humidity is 65%±5%. The natural conjunctiva is very sensitive to changes in temperature and humidity.
