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Restoring Old Paint


224 Peter
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Having returned to modelling after a gap of some 40 or so years some of my Humbrol tinlets, which go back to the late 60s or early 1970s needed checking. Whilst most are in perfect condition a few had succumbed to the passage of time and were what seemed to be beyond help. 

I was reluctant to throw them away. 

But reading through many posts here I thought it was worth trying to recover them. 

 

I bought a "Trumpeter" branded battery mixer and some Humbrol thinners. 

Step 1 was to put about 5mL of the thinners into the tinlet and using a metal spatula cut up the solid paint into smaller bits. I put the lid back and left for a couple of days to soak. 

Step 2 was to put another 5mL in the tinlet and start work with the mixer. The softened paint started to mix, I added more thinners as needed. 

I repeated the process several times over a week or so in so far all the tins have been restored to usable paint. 

 

I was curious: what is in Humbrol thinners? A bit of web searching and I discovered a MSDS, or material safety data sheet. It is issued by Rustins, well known paint makers and probably the UK maker of all the now UK made Humbrol paints. 

What is in it?

80% (70% to 90%)  NAPTHA (PETROLEUM) HYDROTREATED HEAVY: This was not a surprise and is a highly refined light hydrocarbon, with little smell. It is highly flammable. 

20% (10% to 30%) 2-METHOXY-1-METHYLETHYL ACETATE: This was a surprise. It is a commonly known as PMA and mainly used as a solvent for industrial paints and coatings in the automotive industry.
It is also used as a solvent in the electronics industry and formulated into industrial and commercial products. Some specific examples are paints, inks, lacquers, varnishes, cleaners, coatings, etc ink removers.

In the Humbrol thinners it helps keep pigments in suspension and I suspect it is a component of the paint. 

 

So, the recovery of semi solidified Humbrol paint using Humbrol thinners is the solvent of choice, for compatibility and efficiency. 

 

The next stage is to see how Humbrol enamel thinned with Humbrol thinners works. 

The only problem with Humbrol Thinners is the price.. £5.50 for 125mL..about the price of a glass of wine! 

 

 

 

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BUT........................and there's ALWAY'S one!

If you can bring very good Humbrol paints back to 'life', wine definatly takes a 'back seat'!!

 

Joking apart, have you tried to get some Rustins thinner, as a 1 Ltr. 'trade' tin is £13, have a look here:-

https://www.rapidonline.com/rustins-cellulose-thinners-554461

It's even available from Tesco (other retailers exist!) but only 500ml at £8.50

 

Hope this helps,

Paul

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I need to get the MSDS to see what is in the cellulose thinners...

The Rustins sales info says it is not a petroleum product.

 

"Does not contain any xylol, toluene or any other petroleum derivative and is not classified as a petroleum mixture".

 

The Humbrol stuff isn't, from the MSDS, a petroleum mixture, so it could be the same. A lot cheaper. 

 

All this chemistry is part of my working life, I'm an analytical chemist in the "they give you money" world. 

So I can pretend I know what I'm talking about. 

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I have Humbrol paint that has been standing idle for years, some colours we buy for a project and never have a reason to use that colour again, I still have many authentics.  I to use a battery mixer, but some sediments take ages to get unstuck from the bottom having stood idle for a period of time.  What I tend to do, is every now and then is stir some of those paints to keep them fresh, before I do this, I select 3-4 and stand them on a radiator for about 10 minutes(make sure the rad is on!  :)) this soon softens all the sediment in the bottom and I have no problem then stirring them as the sediment has disolved.

 

I also use the "Rustins" thinners, obtained from Ebay sometime ago and use this whenever I need to do spraying, I found its an aggressive thinner and easily thins down the humbrol paints............some paints that are starting to go thick and sludgy I may also add to those paints and found that it works well getting them back to consistancy

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The Rustins Cellulose thinners will dissolve polystyrene, I'm not sure it is something I'd want to add to paint to keep. 

It contains:

Methyl isobutyl ketone

2 Butanone oxime, a derivative of MEK

Ethanol, Methanol and Butanone. 

 

Yes, it will help suspend pigments, but it isn't something I'd want to spray or paint on plastic as it will etch the surface. 

It isn't something I'd want to spray without a proper spray hood extraction system. 

 

Looking through all the Rustins MSDS documents they don't have anything equivalent to the Humbrol thinners. 

 

 

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Cellulose thinners =/= enamel thinners. Cellulose can be used to thin enamels for spraying. If used to thin enamels for brushing, you run a real risk of destroying the model. Cellulose is very aggressive and melts styrene plastic. When sprayed on in light coats with an airbrush it evaporates so quickly that it just isn't an issue. When brushing though, your brush will start to drag the plastic with it.

 

Whilst cellulose thinned enamels spray and adhere extremely well (because it ends up bonded to the plastic), it absolutely stinks and the fumes are distinctly unhealthy.

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Hi Peter,

            as your an analytical chemist would the xylene thinners be a better bet?

Rustins recommend it for regeneration of paint, so while it may not be the same as they

manufacture for Humbrol, it seems it may do a similar job?

If so, the tool centre are advertising it at £6.35 for 500ml!

 

Paul

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The problem I have with toluene, xylene and related cyclic hydrocarbons, including benzene, is they are all far more toxic than the two components of Humbrol thinners. 

Benzene is a listed carcinogen, it should only be used in industry where there is NO functional alternative. The main route into the body is through the lungs and chronic exposure usually results in anaemia and leukaemia.  

toluene and xylene are not carcinogens, but they are toxic. Symptoms of xylene poisoning include headache, dizziness, ataxia, drowsiness, excitement, tremor, and coma, ventricular (heart) arrythmias, acute pulmonary edema, respiratory depression, nausea, vomiting, and reversible hepatic impairment. The main route into the body is through the lungs. 

 

Yes, they are great solvents and will certainly soften and dissolve paint (and some plastics) I wouldn't want to work with them inside a room and I certainly wouldn't spray with them unless using a fully ventilated/extracted spray box, or wearing a proper respirator, not really the way I want to go modelling.... 

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Peter,

I bow to your experience as an analytical chemist!

Knew about Benzene, that's been a know carcinogen for decades.

From (limited) use of Toluene, I have first hand knowledge of the headache's it can cause, :zombie:

sadly, never experienced the 'excitement' :yikes: ! As for the rest, not 'nice' products.

May be worth contacting Rustin's direct, to ask if they do the Humbrol type thinners in larger containers?

 

Paul

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I'm in the same boat as you Peter.

 

Came back to modelling after forty odd years and many of my old Humbrols are rock hard!

 

I did manage to mix one up with thinners and it all looked great, painted a nose cone with it (matt red) and it dried fine.

 

The trouble was when I accidentally touched it after it had dried the paint just dusted off with the consistency of chalk. 

 

I'll have to buy some more. 

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Yes, the use of thinners in 'old' or thickened Humbrol enamel is an art to be practiced. At my first attempt, I must have put too much thinners in or not mixed enough because even though the now thin brush coat went on beautifully, when I tried to apply a second coat, it seem to 'melt' the first coat and that began to peel away from the plastic and break up. I had to give it a good drying with my paint stripping gun set on low (thought SWMBO's hairdrier would be too fierce), sand off the peeled paint and start again. I left the thinned paint out to evaporate a bit and better success on my next try. It took years off my life as I looked at the mess on the model - I began to wish I had just used a new pot of paint but it turned out OK in the end. Good luck with your 'old' paints!

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1 hour ago, Neil.C said:

I'm in the same boat as you Peter.

 

Came back to modelling after forty odd years and many of my old Humbrols are rock hard!

 

I did manage to mix one up with thinners and it all looked great, painted a nose cone with it (matt red) and it dried fine.

 

The trouble was when I accidentally touched it after it had dried the paint just dusted off with the consistency of chalk. 

 

I'll have to buy some more. 

 

That happens when the pigment to binder ratio is too high. The purpose of the thinner is to thin and then evaporate. The binder however stays in the finished paint film.

 

It may be worth trying the recovery of another dried up tin but using minimal enamel thinner to dissolve the dried up pigment such that it's paste-like but not solid, then add gloss enamel varnish (the classical yellowish kind) to bulk up the liquid content.

 

The old fashioned gloss enamel varnishes are ... wait for it ... unpigmented enamel base binder liquid.

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Evening all,

 

I too would be interested to source a cheaper/bulk version of humbrols enamel thinners! Like peter i've com back to the hobby after a break but i'd sold all of my paint.. I started painting with humbrol color and humbrol super enamel at about age six or seven!

 

On return to the hobby i just bought up a load of old made in hull humbrol tins (ebay mainly) one thing to note though chaps.. The old stuff thins fine with white spirit! The issue is that the newer tins wont (made in uk tins onwards) the matting agent goes all streaky and makes a mess of your finish!

 

I dont think humbrols new enamels are that bad barring the rlm range its just it seems as if they specifically need humbrols own thinners, Cheers!!

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After some research it seems that the best "substitute" for Humbrol thinners would be:

 

1L  2-methoxy-1-methyl acetate, (PGMEA):a 1L pack costs about £40.00 from a Lab Supply Company like VWR. 

5L  Johnstones TC2 thinners, a 5L pack costs £53.49 from Brewers. 

 

So, about £94 for 6Litres, plus 24 x 250ml glass bottles with screw caps..., so about £125 in total

The same quantity of Humbrol thinners would cost about £250....

 

Mixing flammable solvents, then packing in 250mL bottles isn't something that can be done at home by anyone.

You need to know what you are doing and have access to a suitable industrial location, like a car bodyshop, where there is ventilation and flame proof areas. 

 

Me? I think I'll just by the Humbrol stuff. OK it is 2X the price but much, much less hassle

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Interesting peter many thanks for that! Im sure i heard someone on britmodeller say you could thin the newer stuff with acetate or naptha?! Can you shed any light on that?

 

I tried thinning a new pot of 86 with white spirit and lighter fuel neither seemed to be much cop..

 

Good thing i got a load of old humbrols very cheap then! Ive got some newer tins but id say they make up less than 5% of my paint stash! For those ill guess ill just have to stump up for the humbrol thinners! Cheers!

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I've ordered some of this stuff to see if it's a viable alternative to the rather expensive thinners available through hobby shops.

 

https://www.ebay.co.uk/itm/VMS-Airbrush-Thinners-200-ml-refill-bottle-for-ENAMELS-Humbrol-compatible/322139149646?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

 

I'll report back once it gets here.

 

Tony.

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Naptha as a generic description for petroleum distillates, the main component of Humbrol Thinners is a very pure, "heavy" cut of naptha, which is C9 to C12 so not too volatile. 

Lighter fluif is a light naptha, with a lower C number, so burns more easily. 

Most enamel thinners are naptha based, ideally for spraying a volatile cut is better, for cleaning and thinning a less volatile cut would work better.

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19 hours ago, degsye39 said:

tried thinning a new pot of 86 with white spirit and lighter fuel neither seemed to be much cop

For clairity,  @224 Peter   means by C , Carbon, and the amount of carbon atoms in a molecule. Peter aid  he  was an analytical Chemist,  but  for  those who are not...

 

C1 = Methane,  CH4

C2 = Ethane C2H6

The H being Hydrogen,   hence the  term Hydro-Carbons.  

Take off a Hydrongen, add a Hydroxl (OH,  Oxygen Hydrogen) and you get C2H5OH,   or ethanol, ie alcohol, 

Propanol  (as in  Iso-propanol, or IPA, is C3H8OH )

etc

Petrol is a mix of these Hydrocarbons,  usually C8 -  C12,

Lighter fuel is light Naptha, about C6,

white spirit is in the parafin C range, about C15,   so is heavier,  and bog standard  white spirit is pretty greasy.

Diesel is C25-30,   Tar is C-45-50,    they are all interelated chemicals, but as you can see, the heavier the molecule,   the less volatile it is.

Have a look on wiki for more. 

 

Higher grade WS is purer,   but you might want to try  artists Turpentine,  more expensive,  but for model use you only use a little. 

I used some for thinning oil based gloss for a shp front,  wnet on like water and after several  coats gave a beautiful finish.

19 hours ago, degsye39 said:

For those ill guess ill just have to stump up for the humbrol thinners! Cheers!

this may no work as well for the older paint,  which has a different formulation,  the modern paint has  to fullfil modern  Health and Safety regs.

 

If you are a dedicated enamel user,   I'd look at getting some Colourcoats from  Soveriegn Hobbies,  which are from user reports  , here are  excellent,  are available in accurate colours,  and their boss, @Jamie @ Sovereign Hobbies  posts here on a regular basis, as shown above.

large scale oil based paint jobs have put me off the enamels,  which I happily used in my youth,  but I really don't like the solvents.  

I use acrylics for domestic DIY jobs if at all possible now too.

 

crickey,   I really must do some  DIY  rather  than wittering away here...

 

HTH

 

 

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Hi troy evening all Bm'ers

 

I mainly use old humbrol and most of it takes one coat only the real stubborn stuff takes thinning with white spirit.. I got lucky on ebay an bought up two huge lots of older humbrol these lots also contained some tamiya acrylics which i flogged! Ive got about a thousand tins! :o i worked out it cost me about 10p-15p a tin after id sold on the acrylics so i am very much modelling on the cheap!

 

I just impulse buy the newer tins! ill try the artists turps though troy good shout mate! And re the WEM enamels i intend to buy some as a bit of an indulgent treat at some point! Will probably get some rlm colors because im just using the humbrol ''equivalent'' at the minute! Ive been looking on the sovereign hobbies page and drooling at the selection though!

 

Ive got maybe 20-30 tins of older colorcoats from an ebay lot but they are ww2 british naval stuff! 

 

Cheers lads! :yes:

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10 hours ago, TonyW said:

I've ordered some of this stuff to see if it's a viable alternative to the rather expensive thinners available through hobby shops.

 

https://www.ebay.co.uk/itm/VMS-Airbrush-Thinners-200-ml-refill-bottle-for-ENAMELS-Humbrol-compatible/322139149646?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

 

I'll report back once it gets here.

 

Tony.

Interesting bud yeah please do!

 

Looks to be a fair bit cheaper than the humbrol option if bought in bulk especially :yes:

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