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The msds for Interlux 333 indicates that it is comprised of 75-100% kerosene, and up to 25% naptha. Instead of paying $52/gal at a marine store for Interlux 333, 1 gal of kerosene fuel at a big box home hardware store (not Home Depot, fyi) costs only $11/gal. Has anyone used kerosene fuel to thin polyurethane brightsides (not the enamel). I'm painting the cove stripe and the weather is turning hot on the Chesapeake; Interulx recommends thinning with 333 in warm weather. Thanks! Bruce
 

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If kerosene is so much cheaper, don't you think that paint manufacturer would just use it and pocket the differece?

The naptha is there for a reason - it's a more powerful solvent.

I can tell you from experience cleaning bottom paint off of paint brushes that mineral spirits does NOT fully clean the brush. I need to use the naptha-containing brushing thinner to dissolve all the paint off the brush.

You can experiment all you want, but you'll just be reinventing the wheel. The paint manufacturer spent thousands of hours of R&D time coming up with the right composition.

If you really want to save money by making your own thinner, at the very least you should duplicate the composition that the mfg reports on the MSDS. Then you'll have to buy some naptha and blend it into the kerosene at the 25% level.
 
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I'm in a similar position, only far from a paint store where I can buy polyurethane paint thinner at any price. If the composition of a paint is oil based, then I think it's OK to use turps or kerosene, but with the polyurethane paints I'm not at all convinced that either would do the job. It has been suggested that xylene may work, but that's no more available where I've been than the right thinner, so we are going to have to wait for Rodney Bay, St. Lucia.
 
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Discussion Starter #6
Thanks for the responses - I didn't expect such a quick reaction. Interestingly, Interlux technical support recommended that I clean the brushes with either Interlux 333 or xylene. I used xylene. Also, fyi, xylene is the predominant component of Interlux 216, which is recommended for cold weather painting. The msds for Interlux 333 provides a range of percentages for the composition of kerosene, 75-100%, which I took to mean that sometimes they use 25% naptha and sometimes not. But that could be the wrong assumption. I imagine naptha will be difficult to locate in the retail market. I'll also check the composition of mineral spirits - which I did not consider previously. Bruce
 

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...I imagine naptha will be difficult to locate in the retail market...
Naptha is available at Home Depot.
...The msds for Interlux 333 provides a range of percentages for the composition of kerosene, 75-100%, which I took to mean that sometimes they use 25% naptha and sometimes not. But that could be the wrong assumption...
They "company line" is that reporting a wide range allows for variability in the product. The real reason is they don't want to give you the exact composition to prevent you from using the MSDS to formulate your own product instead of buying theirs. ;)
 
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The real price comparison is not 333 vs. kerosene, it's 333 vs. Brightsides. How much is it going to cost you to thin the paint by 10% with 333? Next to nothing. The 333 is certainly MUCH cheaper than the paint you're thinning, so you're saving money, aren't you?

Talk about spoiling the ship for the sake of ha'porth of tar. Just use the proper stuff and move on.

I've been using the same tin of 333, and the equivalent from Pettit, for about 3 years now. It lasts forever at 10% of the paint/varnish. Just find some cheap kerosene for cleaning brushes etc.
 

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Naptha is available at Home Depot.

They "company line" is that reporting a wide range allows for variability in the product. The real reason is they don't want to give you the exact composition to prevent you from using the MSDS to formulate your own product instead of buying theirs. ;)
Yeah they have several motives at work....Napha is more volatile and often used when a quick set is desireable. Kero if used needs to be the highly refined grade. Good mineral spirits is compatible with brightsides but as sold tends to be quite variable in formula from brand to brand or even batch to batch.(often true with lacquer thinner) too much naptha tends to reduce gloss. Too much of any of them degrades the cohesion of the resin which is the basis of the paints durability. One of the nicest tricks is adding a bit of Penetrol which was used like the magik elixir by boat yard painters with the early poly paints in the early to late seventies...they often achieved mirror finishes by brush application. quite an art!

Sent from my SAMSUNG-SGH-I317 using Tapatalk
 

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... Kero if used needs to be the highly refined grade.....
Knowing where Kerosene comes from, that's a very good point.. hence there's no way I'd even contemplate using store-bought kerosene for thinning paint.

Aside from the effects of the dye additive, there's likely to be trace quantities of water, particulates, 'diesel bug' and all kinds of other goodies in there that don't affect it's burning properties in the least but are very likely to affect the quality of your paintwork.
 

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It bugs me that the paint manufacturers repackage a mixture of common solvents and then increase the price 400%. $52/gal for Interlux 333 vs. $11/gal for kerosene is a substantial difference. If I could buy only the amount that I need, then you are correct that it is a relatively small investment; but that I must buy at least 1 qt. (333 sells for $32/qt.!), which will sit in the can for several years seems like a waste of money. I appreciate your thoughts on the subject - thanks! B.
 

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It bugs me that the paint manufacturers repackage a mixture of common solvents and then increase the price 400%. $52/gal for Interlux 333 vs. $11/gal for kerosene is a substantial difference. If I could buy only the amount that I need, then you are correct that it is a relatively small investment; but that I must buy at least 1 qt. (333 sells for $32/qt.!), which will sit in the can for several years seems like a waste of money. I appreciate your thoughts on the subject - thanks! B.
Short answer: You own a boat. $32 is one of the least expensive things you'll buy for your boat, and a lot less than the paint that it is going into. And a quart is about the smallest quantity that it is feasible to package. When you add in the usefulness of this material for other things such as dewaxing your hull and cleaning your brushes, you'll find it to be money well spent.

Long answer: You are paying for a lot more than the cost of raw materials in that can. You're paying for the R&D that goes into determining the optimum blend of solvents to work in a broad variety of paint compositions and environmental conditions. You're paying for the tech support guy that you called at Interlux. You're paying for the quality control that ensures that the can you buy today is the same as the can you bought two years ago. You're paying for all the regulatory requirements for the manufacturer to ensure that the product is safe in use, during shipment, and when disposed of. You're paying for the implied warranty that using genuine Interlux thinner will insure that you don't ruin the much more expensive Interlux paint that you're adding it into.

Nobody is stopping you from using the kerosene. Go ahead and take your chances. But if you want assurance that the product will work right, you might consider paying the $32 for that assurance.

Disclaimer: I've spent my entire career doing R&D for paint and ink manufacturers.
 

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PhD Chemist here...

Some of the points made during this thread are spot on. The MSDS for the Interlux stuff must include the actual formulation amounts, but generally it gives a range to allow formulation variances and allows the vendor to protect the actual formulation. We do it all the time. 75-100% is a huge range for a specific component, especially one that has a wide range of boiling point, evaporation rate, etc. properties.

As far as blending your own, you can do that, but bear in mind that Kerosene is a pretty generic petroleum product and varies in composition and purity significantly. Same thing with Naptha, Mineral Spirits, Xylenes, etc. When burning these to produce heat and energy or used as a cleaning solvent, the composition isn't that critical but if using as a paint thinner, it could be. Generally, high purity, filtered grades (more expensive) are used when used as solvents in coating formulations. Your store bought stuff is probably one of the lowest grade (less purified, non-filtered) versions, hence the cheaper price.

While I am all for the "Less Expensive Approach" in a lot of cases, for thinning expensive formulated paint, I'd buy the specific thinner that is designed to be 100% compatible with the paint.

DrB
 
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