shellac under oil [Archive]

3 toed sloth

30th March 2017, 04:32 PM

Hi all, sorry if this has been asked before. I'm going to use Kunos oil on a project I'm doing, and I was thinking it may be a good idea to do a light coat of shellac first like a sanding sealer. I don't have a great understanding of how these things work but the oil instructions usually say the first coat has to be left a while before wiping off, so it can soak into the timber. So my question is will the shellac base affect the absorption of the oil into the timber, and secondly, does it matter.

Any comments and advice welcome and appreciated.

Peter

justonething

30th March 2017, 05:23 PM

A sealer seals the pores, so absorption and penetration is greatly reduced afterwards. Some people do it because they don't want their timber to darken. By diluting your shellac with alcohol, you can control the amount of absorption can be had and hence the final tone of the finish.

AlexS

30th March 2017, 05:50 PM

This is my standard finish. I sand to 800 grit, then use a coat of fairly thin shellac as a sanding sealer. This raises the grain. Let the shellac dry, if possible for a couple of hours, then sand again with 800. Clean the dust off with white spirits on a paper towel. When dry, apply a flood coat of 50/50 Kunos oil and Bio-thinners. Allow the coat to sit for 15-20 minutes, then wipe off any excess. You'll see that most of the oil has soaked in. The next day, apply a fairly wet coat, and after about 15 minutes, buff it with a soft cloth. On the third day, apply the mix with 0000 steel wool, then wipe off the excess straight away. After about 15 minutes buff it. From then on, just rub in very light coats, one a day, with a cloth just slightly wet with the oil/thinners mix. You can do this as many times as you like, with some timbers you will be able to get a high gloss if you want.
The old advice was to oil it once a day for a week, once a week for a month, once a month for a year and once a year on your birthday. One client does this with a camphor laurel blanket box I made for her, and after a few years it now has a deep satin sheen.

Sturdee

30th March 2017, 06:19 PM

The best would be to contact Livos (https://www.livos.com.au/) direct, they are very helpful if you have queries, but I think you would not use shellac first but instead follow these instruction. (https://www.livos.com.au/uploads/192/83/App-Int_Furniture.pdf)

Peter.

3 toed sloth

31st March 2017, 06:05 AM

Thanks, Alex, it may have been one of your previous threads which got me started thinking about this whole thing. I like the depth which shellac brings out but I want an oil finish for this table I'm making so this seems like a good way to get both. In my head filling or sealing the surface just sounds like nothing can soak in afterwards, but your explanation of the first oil coat soaking in after shellac sealing, shows this isn't the case. I tend to take things very literally and as a plumber, when something is sealed it is sealed, nothing gets out or in. I suppose "sealing" a timber surface has a different meaning.

Thanks, Sturdee, I have done a couple of things following the instructions, and the results are good but I'm just exploring the possibility of getting a bit more depth out of the finish, and the shellac sealer also addresses raising grain.

Another thing, Alex, the instructions suggest not sanding below around 180 - 280 grit as finer sanding can glaze the surface and affect oil absorption. I did a trial piece, sanding to 240 grit, and wasn't happy with the result. You sand down to 800 grit, and I know you have made many beautiful pieces, so what are your thoughts about the glazing theory?

Peter

AngelaPetruzzi

6th April 2017, 04:58 PM

Everybody has their own way of finishing off projects and if one way works for you and you achieve the look that you are after, then that is great.

From our working with the products, being penetrating oils, the oil molecules need to connect to the pores of the timber. (Unlike synthetic coatings where the molecules are large and sit on top). The finer the sanding grit, the more closed the pores become (glazed over) the less oil that penetrates. The theory of diluting it with thinners comes from the boiled linseed/thinners mix of the home handyman. This does not necessarily allow the boiled linseed to penetrate deeper. The Livos oils are cold pressed linseed oil with other waxes and resins. It does not need diluting as it compromises the product. Especially it being certified food safe.

On small projects, ornaments etc, it is not as critical as say a table top. Hard wearing areas such as these, require full penetration of the oil wax resin mix and we don’t recommend a very fine final sand. By leaving the pores more open allows the oils to penetrate as they should. One can achieve a “finer finish” by buffing in-between coats with something similar to a scotch brite. This has nothing to do with the fibres but it does flatten the wax crystals in the oil, giving it more sheen level and starts to build up the “fine furniture feel” of a higher sanding grit.

If one does apply either shellac or other product, this only blocks the pores, again stopping the oil from penetrating. As the oils are applied with excess wiped off, there is minimal benefit in using anything prior to oiling. Also, most woodworkers and furniture makes find 3 to 4 coats on consecutive days ideal.
Remembering, there are no synthetic hardeners so if it is for a table, the coating needs to harden and cure before it repels water and or stains. one can still use it though, just be a little more vigilant with spillages etc.

As said AlexS, if you are happy with your process, please do not discontinue. The main thing is it is achieving the look that you are after.

george mavridis

6th April 2017, 07:31 PM

[QUOTE=AlexS;2015613] Clean the dust off with white spirits on a paper towel.

What is the difference between white spirits and methylated spirits?

AlexS

6th April 2017, 10:33 PM

White spirits is similar to shellite - it is not as volatile as methylated spirits, and also, it won't dissolve shellac.

White spirits
409907

Methylated Spirits
409908

george mavridis

6th April 2017, 10:38 PM

Thanks Alex

ian

7th April 2017, 01:04 AM

also,

white spirits is a petroleum distilate -- from memory a mix of hexane (6 carbon atoms in a chain), heptane (7 carbon atoms) and octane (8 carbon atoms). Back when my now deceased father was working, his lab used hexane as a solvent and I used to get the "waste" hexane to use as a white spirits substitute in my camping stove.

mentholated spirits is an alcohol.

3 toed sloth

11th April 2017, 06:06 PM

Thanks, Angela, great information. In my mind I'm thinking there may be a trade off between maximising oil absorption by only sanding to 240 grit, as opposed to maximising the fine finish by sanding to a finer grit. I have sanded the legs and aprons for my table down to 400 grit but haven't oiled them yet. I'll be able to compare the results with my 240 grit test piece. These areas aren't so hard wearing so not critical for oil absorption as you explained.

For the table top I can see your reasoning with the hard wear and need for maximum absorption. I have been using 0000 steel wool for the buffing between coats so maybe a scotchbrite pad, as suggested, would be more effective. I haven't used scotchbrite pads before but I seem to remember there are different grades? Which is the best one to use for the buffing between coats?

With thanks, Peter

Kuffy

11th April 2017, 07:04 PM

FWIW, I just finished up the third and final coat of my own mix of BLO/poly/turps which I applied on top of sanding sealer. enough time hasn't past by yet to see if I have any adhesion issues, but it looks good at the moment. And the best part was after I had lightly flooded the surface and waited 10-15mins and wiped off with a rag, I was able to walk away (goto bed and come back tomorrow) and there was no regurgitated oil spots which had seeped back up to the surface like what happens when applying oils to raw timber.

truckjohn

12th April 2017, 12:30 PM

Just a caution from my own experience.

I used shellac as a sanding sealer, then varnished over it with a short oil varnish product. (Conventional varnish - not poly)

Some time later - I had huge issues with sections of the varnish finish peeling off of the shellac. Worst were problems that saw bumps/impacts. The varnish would peel right off in little fish scales.

Complete catastrophe. Some people have mentioned that I probably needed to wash it down with turpentine and mineral spirits - to remove any residual waxes, then lightly sand with 320+ grit to give the varnish something to grab...

but honestly - I dont think I will do it again unless I have serious varnish curing issues that I cant deal with via wiping a thin coat and giving lots of UV light... Rosewood is one such problem child.... But it can usually be dealt with by wiping a super thin coat and them giving lots of UV (sunlight) till it cures hard - then do another wiped coat and more UV repetitions till its happy curing right.

Now - I just apply my oil finish straight to the wood and off I go.

AngelaPetruzzi

24th May 2017, 12:27 PM

I'm sorry for not replying earlier Peter..(3 toed sloth interesting name) and hope you did call us for an answer. As long as the scotchbrite is non abrasive you can play around with various grades. When we do floors, we use the glowmesh white polishing pads.

3 toed sloth

26th May 2017, 04:53 AM

No worries Angela. I have now glued up and finished the table legs and aprons, still making the top. I'm just a weekend warrior so things take a while:rolleyes:

I decided to sand down to 400 grit. Then on the first coat, as per instructions, I took care to make sure surface was fully saturated, adding to areas that soaked in too quickly, so surface was really wet. Then added the next 2 coats strictly as per instructions. I ended up getting some gold Beartex pads from Sandpaperman which are very fine, about 1000 grit equivalent. Lightly rubbed with these between coats. I am extremely happy with the results.

I still have a lot to learn about finishing but with the help of the people on this forum ( I don't actually know any woodworkers) I'm realising there's a lot more to it than just shellac, oil and polyurethane. There's a personal ingredient that can't be measured or instructed but is developed with practice, trial and error.

Thanks, Peter