Thinning Paint.........Advise Please

Robbie uk · 18 Jul 2012

What does Zampa know !!!! LOL........

Paintbrush · 23 Jul 2012

Question; Does as paint brush act as a wick soaking up white spirit?

Answer; Yes, this had me puzzled as I couldn't understand why white spirit was dripping constantly from my brush when inverted.

I thoroughly cleaned and dried brushes with paper towels ect but then used the brush to mix in the white spirit to thin the paint.

It was ok while using the same colour (white) but switching to blue then back again the blue pigment leached back into the paint.

I guess it must soak into the brush under the stainless retainer.

Will it still soak up the white spirit even though it's mixed in well?

Cheers,

joe-90 · 23 Jul 2012

errr - you don't use your brush for mixing.

Paintbrush · 23 Jul 2012

Sorry, when I say mixing it was one of those mini gloss roller trays where I added a drop then pushed it back and forth.

Will a brush suck out the white spirit?

Zampa · 23 Jul 2012

joe-90 said:
errr - you don't use your brush for mixing.

Nope but a lot of painters still do for some reason..really bad practice

Paintbrush · 1 Sep 2012

Paintbrush said:
Will a brush suck out the white spirit?

The answer to this is yes.

At first I thought the white spirit must be in the handle as even when thoroughly dried it still dripped up the handle in a vertical position.

This happened with water based paints too. Once it's thinned the brush acts like a filter holding the paint but letting through the carrier !

TheDec · 1 Sep 2012

Well the answer is actually no, the brush is an application device which in the correct hands becomes an extention of the hand. When primed and dipped into a correctly mixed paint or varnish it would then achieve these factors.

Thus when you say that the brush sucks out the spirit thus causing it to flood the stock of the brush and escape down the handle can be described as two fold, either the system was badly prepared or the brush was overloaded.

Dec

Zampa · 2 Sep 2012

Paintbrush said:
Paintbrush said:

Will a brush suck out the white spirit?

Click to expand...

The answer to this is yes.

At first I thought the white spirit must be in the handle as even when thoroughly dried it still dripped up the handle in a vertical position.

This happened with water based paints too. Once it's thinned the brush acts like a filter holding the paint but letting through the carrier !

Yep...Ive seen this happen many times..more so when a synthetic brush is involved for some reason, probably down to the non absorbent and smooth qualities of the filaments creating a capillary action, thus drawing any excess white spirit up..
Thats why its vital that the paint is correctly prepared first. Ive seen people using their paint brush as a 'stick' before..bad practice and one im always warning my trainees about.

Paintbrush · 7 Sep 2012

Sorry Dec, I am with Zampa on this one as it's happened too many times.

Capillary action is definitely a force here, although I accept more experienced users would be aware of this issue to start with.

Overall, I am very happy with the outcome, with several visitors commenting on the quality of finish.

Cheers for everyone's input along the way.

Zampa · 11 Sep 2012

Yeh nice adverts luv..........

Miss k · 16 Jun 2018

Zampa said:
There are two types of paint, trade and retail, in general retial paint doesnt need thinning...trade formulations sometimes do.

There are various reasons for thinning paint, some paints are 'sticky' when your trying to appy them, especially oil based glosses...so you need to add a drop or white spirit to them (not turps substitute, which can have an effect on the sheen of the paint)

Sometimes the paint is two thick...this is often common with some undercoats, if its too thick it will leave brushmarks..so it need thinning

It is also hard work using a paint thats too thick...again a little thinners makes it easier for the person putting it on

Another reason is to allow a paint to semi penetrate a surface, I have just done an outside job, new rendering, the first coat which was an oil based masonry paint needed to penetrate the surface, this enables it to 'lock' on the surface and provides a good based for subsequent coats...so I used 15-20% white spirit

Some surfaces like rendering are porous, which causes the paint to suck into them...thus making it hard work to apply and youl end up using to much paint (which doesn't penetrate or prime and just sits on the surface)

The other and maybe most obvious reason it to help make the paint go further...(hence white spirits nickname...'doomore') it will help to a certain extent but the type of surface will have a bareing on this, imagine a gallon of water and a gallon of slightly thinned paint on a plaster surface...the paint allthough thicker will go further becasue the water being thinner will be absorbed more into the surface....so thinning paint paint purely to make it go further in order to save money doesnt always work plus, by thinning it you are reducing its covering power.

Most painters beleive that it far better to give something two decent coats than having to give it three because the second one has failed to cover.

When you thin an oil based paint you are breaking down the carrier oil and resins..remember that the highest percentage of gloss paint is this oil....think of it as a varnish with with powder in....if you break the oil down in gloss paint to much it will go flat

Too much thinners can also have an effect on the binder in a paint...the binder holds the pgments together...it this happens the surfac of the dried film will become chalky and powdery

Water based paints acrylics, masonry etc...thin with clean water

Oil based, gloss, undercoat etc...thin with white spirit

There are also some speciality paint that have their own types of thinners...hammerite for example

Hope that helped.

Miss k · 16 Jun 2018

I know this is an old post but thanks you so much for this explains everything I needed to know and more.

opps · 17 Jun 2018

Miss k said:
I know this is an old post but thanks you so much for this explains everything I needed to know and more.

Which part in particular was helpful?

Sorry, I am not part of the Spanish Inquisition, it just might help someone else that has the same question(s) as you.

*******EDIT**********

Sorry, only just notice that you quoted the post that you found informative.

I would however add that there are paint additives that help paints flow without actually thinning them.

I use Floetrol to extend the "wet edge" when working with water based finishes and Owatrol when working with oil based finishes.

Both products are made by the same firm.

https://www.owatroldirect.co.uk/product/floetrol/

https://www.owatroldirect.co.uk/product/owatrol-oil/

Neither product is cheap but both are indispensable if you want to achieve a high quality finish.

If working with oil based paints (post 2010 VOC compliance) I would also recommending adding a little bit of terebene- it will speed up the curing time but won't hamper the application of the paint.

Miss k · 17 Jun 2018

The part about some undercoats can be to thick and you can see the brush marks thru it and by thinning it slightly it helps with this. I always have had that problem when paint doors and was looking to see how I could avoid this problem, also using a roll to do doors Aswell,

opps · 18 Jun 2018

Miss k said:
The part about some undercoats can be to thick and you can see the brush marks thru it and by thinning it slightly it helps with this. I always have had that problem when paint doors and was looking to see how I could avoid this problem, also using a roll to do doors Aswell,

Sorry, I was in the process of editing my post when you replied.

Rolled doors, please no. Sorry, one of my (many) pet hates. Rolling (IMO) is acceptable as a delivery method but a proper door should have tramlines (subtle brush marks) that run in the direction of the wood grain. With the right paint additives you can use a roller to apply the paint and then a decent brush to create the tramlines (running the brush over the rolled surface).

With regard to panelled doors, I honestly can not see any reason for using a roller.

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Thinning Paint.........Advise Please

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