shellac+wetting+agent

[justwantin]

I've been experimenting with spraying shellac on Japanese timber framed lanterns and the results look promising with the exception of sometime dusting from shellac partially drying before contact with the timber. I spent some hours searching on the net yesterday and found that there are wetting agents for shellac sold in the US but also that shellac drying time can be retarded by adding turpentine.

One post on a US forum quoted a Fine Wood Working article on finishes and a ratio of 1tspn turps to 4ozs shellac. That works out to 5ml/120ml or 1/24.

Does anyone here have experience using turps as a wetting agent ? and if so at what ration?

[ubeaut]

Initially try using less shellac and more meths in your spray. Do light coats rather than heavy coats. This should dry quickly and any dust particles should wipe off when dry. You appear to be getting overspray from the shellac.

Anyway... Turpentine does work to a certain degree as a retarder, but n-Butanol is the best thing to use.

Problem with n-Butanol is that it isn't readily available in small quantities in Australia. Try contacting Recochem CLICK HERE and see if they have distributors selling smaller than 200 lt quantities.

I have some for my own use. May be able to get some for you if needed. No idea on price. Many US manufacturers incorporate it in their premixed shellac.

Hope this is of some help.

Cheers - Neil

[justwantin]

Thanks for the reply Neil. I'll have a look at sourcing n-Butanol

I must admit that 1) I'm a novice sprayer and 2) to date I have not been very scientific when mixing batches of shellac.

Yes, my shellac mixes to date may have been light on the metho. Next go I'll be starting with a one pound mix which I recon to be ~950ml metho to ~.454kg shellac flakes as a starter then test without gum turps and with at 5ml/120ml (1/24). I found another ratio of 1tbsp/1qt ( 15ml/946ml or 1/63) but they don't provide the cut used whereas the first one was given with a one pound cut.

I have tried using an air brush, a mini siphon sprayer (paasche-62) and a small gravity feed touch up gun but over spray is difficult to eliminate or minimise on my laterns as what doesn't land directly on one panel/side will land on the adjacent or opposite panel/side of lanterns. This is a probably first a problem of my technique and secondly shellac metho with or without wetting agent mixture. Its hard not to hit one side and not the other. Here's what I'm spraying, paper is applied after finishing: http://andonsline.com/products/other...er-andons.html

I have also read on US websites that a wetting agent will also reduce surface tension which can result in excessive build up on hard edges. This is also an issue for me but I didn't want to complicate my original post like I've just done with this one :^(

[ubeaut]

Try a mixture of 220gm to 1 litre Industrial Methylated Spirits 100%IMS is best but 95%IMS is fine. If the bottle doesn't say 95% or 100% on the label, don't use it. This could contain up to 40%+ water. To me called Methylated Spirits it has to be OP (over proof) this meand it must burn when ignited. Metho will burn with around 47% water in it (or something like that) Good for washing windows etc but useless for shellac.

Do not put turpentine into the whole lot but into a trial lot in your gun. And it they are talking about turpentine in the US then it more than likely won't be mineral turpentine they're talking about but pure gum turpentine. Try and suss this out if you can because mineral turps over there is more likely to be referred to as white spirits.

The 220gm to 1lt is roughly the equivalent of a 2lb cut use this as your base and cut what you need to use with meths (at least 50/50). Only cut what you need not the whole litre.

Cheers

[justwantin]

Thanks again for the reply.
Diggers metho spec sheet says ethanol >=95% water <=5%. I would have thought an unopened bottle would be good enough. I had planned to use Diggers Pure Gum Turpentine.

Your caution and advice is most welcome :^)

I'll revert when I've had a go, might be on the weekend though

[rob streeper]

Thanks again for the reply.
Diggers metho spec sheet says ethanol >=95% water <=5%. I would have thought an unopened bottle would be good enough. I had planned to use Diggers Pure Gum Turpentine.

Your caution and advice is most welcome :^)

I'll revert when I've had a go, might be on the weekend though

If you want to dry ethanol there is a very easy way forward. Get yourself some Epsom salts. Put a nice layer of aluminum foil on a cookie sheet , spread the Epsom salts over it in a thinnish (!1 cm thick max) layer and heat it in the oven at about 120 C for two to four hours depending on how much salt you use. Near the end of the baking take a 1L mason jar and put it in the oven to dry it too - it only needs about 15 minutes. At the end of the heating period turn the oven off and leave the oven door closed. Let the oven cool down to the point that you can handle the contents without burning yourself. Remove the dried Epsom salts and place them in the dried mason jar and cap it off.

When you want to dry some ethanol take about two tablespoons of the dried Epsom salts and add it to a liter or so of 95% ethanol. Shake it well every couple of hours or so through the day and leave it sit overnight. The next day carefully pour off the amount of ethanol you need and cap the jar containing the now thoroughly dried ethanol.

When you have used up all of the dried ethanol you can recycle the Epsom salts by first allowing all of the ethanol residue to evaporate and then baking the salt as described above.

If you don't want to use Epsom salts you can also use Gypsum from wall board if you strip off the paper covering. It is calcium sulfate and the effect is the same but you need to use about 3.5X the mass to get equivalent drying power.

The same trick can be done using the silica prills from disused dessicant packs if you have enough mass to do the job (50gm/L).

Be careful, no ethanol or any other flammable stuff in the oven.

Cheers,
Rob

[ubeaut]

Yeah drying ethanol.... What fun. What ever you do don't drink it. Pretty sure it doesn't get the denaturant out as well which is often methanol and you know what happens in Bali when they serve drinks laced with methanol.

The old wino's back in the day used to get a whole loaf of bread and bite a corner off the top and the opposing corner off the bottom of the loaf then slowly pour the methylated spirits through the top hole to have it come out the bottom hole into a receptacle as supposedly pure alcohol. No wonder so many of them died a horrid and lonesome death.

Go buy 95% that's fine. You can't actually get 100% pure ethanol (Methylated Spirits) without having a pharmaceutical or medical licence. We only use 100% IMS for our shellac and friction polish because as little as 5% water can stop our waxes from blending with the shellac. Our 100% contains 0.9% denaturant to make it unpalatable. Any water or other pollutants will be due to careless handling or miss treatment. Leaving a jar of metho uncovered for a day can add dramatically to the water content especially in damp or humid weather.

Cheers - Neil

[rob streeper]

Leaving a jar of metho uncovered for a day can add dramatically to the water content especially in damp or humid weather.

Cheers - Neil

The method I described can be used to keep the water down in you ethanol too. Wrap the dried Epsom salts in a cheese cloth, tie it off making a little bag and drop in the ethanol. It will absorb the water that the ethanol absorbs from the air and keep your solvent in good shape for shellac work.

[justwantin]

I don't think I'll do any extreme drying. Previous mixes were with newly purchased unopened bottles. Any balance would be consigned to cleanups. Even though spec sheet says 95% I'd not be surprised if it was minimaly less. Still my problem is drying too fast and surface tension which would imply a higher rather than lower alcohol content, or so I would expect within a given range.

[rob streeper]

I don't think I'll do any extreme drying. Previous mixes were with newly purchased unopened bottles. Any balance would be consigned to cleanups. Even though spec sheet says 95% I'd not be surprised if it was minimaly less. Still my problem is drying too fast and surface tension which would imply a higher rather than lower alcohol content, or so I would expect within a given range.

The reason that ethanol is frequently sold at 95% concentration is that it forms a low boiling azeotrope. The azeotrope of water/ethanol is 95.6% ethanol and it boils 0.3 C lower than the boiling point of pure ethanol (78.5 C). Thus your ~95% ethanol actually evaporates more rapidly than does dry ethanol.

If you want a slower dry time and n-butanol is difficult for you to get you can use isopropanol (dry, b.p. 82.5 C) to cut or even replace your ethanol. The highest concentration of isopropanol available at the consumer level is typically the 91%, which is the water ispropanol azeotrope. For shellac work this must be dried prior to use. Another possibility is n- or 1-propanol. It has a b.p. of ~98 C. Ebay lists n-propanol at $19/liter.

[soundman]

Like most laquers.... finishes that set up by solvent evaporation alone...I would have thaught that going to a mix containing much more solvent would solve many of the over spray issues, because the over spray would be wet rather than dry and would melt in or flow out rather than fly as dry or part dry material.


I know a lot of people spray nitro (myself included) way higher than the rocomemded 10% thinning rate...more like 50% to 70% thinner for that very reason.
Many very light coats or several passes in the one spraying.

The more solvent, the slower the resin will dry and the more likley that over spray will blend in.

Wth most of the evaporative finishes... shelac especially there is little or no issue with the resin being devided too much by the thinner.


cheers

[soundman]

Oh another trick I have had partial sucess with on nitro, is spraying over with solvent alone.

One needs to be a bit carefull there is a fine line with how wet the solvent needs to be on the surface and there is some delay in the flow out...but it may transfer across to shelac.

cheers