Usually hydrometer gives correct readings when only water and alcohol is used. The readings change even if the font solution is added to this mixture of water and alcohol.
usually the chiller tank is contaminated with ink, paper fluff etc during press runs.
Get a good filtration system and clean the solution. If it's so "polluted" that you cannot take accurate measurements you have other problems, like the reason for the excess contamination
What temperature are you maintaining your fountain solution. Gravity readings are temperature sensitive.
Most contamination sources will not effect the specific gravity much, solvents will lower it, soluble salts will raise it. Non water soluble debris will have no effect. Do I read you correctly when you say that the hydrometer comes completely out of the solution? What range is your hydrometer?
Whose thermal plates are you using? Thousands of printers in North America have been successfully using alcohol substitutes for years and years on all kinds of plates including thermal, so what's the problem with yours?
If you want to run alcohol free get some help from the press manufacturer and your suppliers. Two of the things you will need is a good filtration system and good quality dosers for the fountain concentrate and alcohol suibstitute. You will never have to use a hydrometer again, measurements will only be made for pH and conductivity.
Do you have a problem with the hydrometer? Can you calibrate it? In raw water from the main, DI, Distilled or RO water it should read zero. Like wise in your standard correct mixture of fountain concentrate and water (no alcohol) only it should still read zero.
I've seen how the instrument works. It isn't as simple as directly reading the bar as directed on the contaminated fountain solution.
You also required to know the the density of your fountain solution together with a chemical drop test on your fountain solution to get the alcohol content of your fountain solution. The drop test counts the number of drops of a specific chemical when mixed to the fountain solution to become pinkish colour.
The aerometer that bottcher was advising me is the only correct way to read the % of alcohol content in the fountain solution ( especially on contaminated fountain solution); provided that the fountain solution is not dark in color where you would not be able to spot the pinkish appearance when doing the chemical test.
Sounds like you have other issues, invest in a good filtration system that thoroughly cleans the fountain solution removing all the 'stuff' that is contaminating it. Investigate what is contaminating it so badly that you cannot take reliable readings. Investigate why you cannot go Alcohol free and eliminate the issue as millions of other printers have with your type of plates. If the solution is getting so contaminated would'nt your conductivity climb through the roof.
I've seen how the instrument works. It isn't as simple as directly reading the bar as directed on the contaminated fountain solution.
You also required to know the the density of your fountain solution together with a chemical drop test on your fountain solution to get the alcohol content of your fountain solution. The drop test counts the number of drops of a specific chemical when mixed to the fountain solution to become pinkish colour.
The aerometer that bottcher was advising me is the only correct way to read the % of alcohol content in the fountain solution ( especially on contaminated fountain solution); provided that the fountain solution is not dark in color where you would not be able to spot the pinkish appearance when doing the chemical test.
Thank you very much, got the point, will get in touch with bottcher to understand how to go about it.
Being a prepress service bureau asking my customers to install filteration systems is not a practical option neither they would convert themselves to go alcohol free.
The reason I wanted to know was that none of my customers know how much alcohol was going into the chiller tanks when they were topping up and not preparing fresh font solution.
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Originally Posted by lilgap84
