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Ankush Sharma
Ankush Sharma • Oct 11, 2016

What is the use of Thinner and Hardener in paint?

Hello Everyone,
We all know that, before painting we have to add thinner and hardener in paint.
But i want to know few things.
1. why there is a need of thinner in paint? Usually, the simple answer for this question is to make the paint thin. But, if this is the case then why don't paint manufacturing company's just manufacture the paints thin at first point? So, there must be some technical reason to add thinner in paint! what's that?

2. Why we add hardener in paint? Even i read somewhere that its not compulsory to add hardener always. So, first thing that what is the use of it in paint? and if it's true that it is not compulsory in all cases then how can we come to know?
1. Thinning the paint is a point of use issue. Adding thinner to paint increases bulk, packing and transportation costs. Customising the spreadability at the user end is lost. Thinners are a fire hazard, which may add to transportation and warehousing problems.

2. Hardeners are needed only for two component type of coatings like epoxies that cross link. If a particular paint needs it the manufacturer supplies it. Since there is a pot life after adding the hardener, this has to be necessarily done at use.
Ankush Sharma
Ankush Sharma • Oct 13, 2016
A.V.Ramani
1. Thinning the paint is a point of use issue. Adding thinner to paint increases bulk, packing and transportation costs. Customising the spreadability at the user end is lost. Thinners are a fire hazard, which may add to transportation and warehousing problems.

2. Hardeners are needed only for two component type of coatings like epoxies that cross link. If a particular paint needs it the manufacturer supplies it. Since there is a pot life after adding the hardener, this has to be necessarily done at use.
Ok, Thanks for information.
You gave all the information regarding at what time thinner and hardener is added and why it is added at that particular time.
But one more thing i want to know, Why there is a need to add thinner and hardener(in case if it is specified by manufacturer) in paint? Simply, why these are required in paint? Do, they increase the life or finishing of paint( because I don't know for what purpose these are) or may be any other technical reason?
Thinner does what its name implies. It reduces the viscosity of the paint. Depending on the method of application (Brushing, Roller etc.) and thickness of the coat the user can adjust the consistency to suit the demands of the job.
Some paints have a chemistry that requires cross linking between two types of molecules. One will be the resin in the bulk paint. The other molecule is in the hardener. When the paint is mixed with the hardener the cross-linking chemical reaction begins. That is why a pot life is specified. If you wait too long after adding the hardener the paint will set and not usable.

Some basics about non cross-linked paints here:
https://gaganshreeagarwal.webs.com/painttechnologybasics.htm

This discussion on hardeners may help you:
What is "hardener" in paint for?

What if I use a wrong hardner with a paint??

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