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grain filler, not rustins or aqua coat please  

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simon1138
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01/09/2020 12:00 am  

hello,

i have some oak i found in a skip and cut it into a body. only problem is the grain. i have tried some wood filler that i added water too. it seemed to work a bit but i would like to try something else. i watched a video on youtube of a man "making gravy" with oil and orbital sander. spread on some oil, start sanding and in no time the man had a "gravy" of sanding dust and oil to fill grain with. this is an american video so he mentioned armourall or something. i have boiled linseed oil which i heard should work. i have a book on finishing but its american and talks of shellac and denatured alcohol which i believe is methylated spirits? and some stuff in the book seems to contradict what others say. i would like to find all the possible (cheap) ways to grain fill. i thought that maybe primer would work. aqua coat is expensive and that rustins stuff seems to be problematic, oil based, drys up in tin, not much there for cost.

i will give the boiled linseed oil a go and see what happens and report back but until then any advice on other grain filling methods. i am going to start with a 100 grit, 150, 240 then 400 to make the gravy. all using an orbital sander. 


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John L (Boo)
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01/09/2020 9:03 am  

Not heard of grain gravy before, let us know how you get on and try not to eat it! 

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tv1010101
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01/09/2020 9:58 am  

Similarly, "grain gravy" is a new one on me, but it's probably just an Americanism.

I *am* familiar with the wet sanding technique.  You sand with oil, rather than with more normal dry sanding paper.  That creates a slurry of oil and sanded material which you then need to clean off the body with a rag.  But the process of both sanding and then wiping the slurry away effectively fills the grain (and any other imperfections in the wood) with the slurry, which then dries off to leave a beautifully smooth finish.

I've not used power tools to do the sanding before - just good old elbow grease.  (Careful not to mix any grease with the slurry).

It's difficult to show in photos, you really have to feel the wood to feel the different - it leaves a finish as-smooth-as.

Obviously that's better when you're planning on an oiled finish rather than any sort of stained/painted finish.

 


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simon1138
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01/09/2020 8:04 pm  

hello,

i tried the "gravy" method today. i used my orbital sander and went from an 80 grit, 120, 150, 240, 320. then using 1200 wet and dry, mentioned in the youtube video, i poured some boiled linseed oil onto the wood and started sanding. after a few minutes of sanding i removed the orbital sander and using a plastic card swiped across the wood. there was a brown liquid which i took to be the gravy. the video mentioned using a 1200 grit so you get a small amount of dust as possible to fill the grain. i smoothed the gravy across the wood and it seemed to fill the grain and cracks. i have left it to dry for about an hour and the grain is still visible and you can feel it. i read about the slurry method which is the same thing, on a different site. but that guy uses regular sand paper, 100 grit, covers the wood in oil and starts sanding. then uses a burlap bag to wipe the oil into the grain. i dont know why a burlap material. i think maybe i will try again and leave a layer of gravy/slurry on the wood and let it dry. i know that if it hardens it will be a case of sanding it smooth but i am not sure what else to do. any advice on this would be great.

thanks

simon


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tv1010101
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01/09/2020 8:26 pm  

Oak is an unusual wood to use for guitar bodies.  It’s usually quite dense / heavy.

Thats an aside really, but worth double checking before you end up with a guitar too heavy to be comfortable.

I would have thought that a powered orbital sander would have made quite a mess, pushing the oil *off* the body rather than creating a dust/oil mix on the body.

Hand sanding might be more effective in that you might create a better mix of dust and oil, which gets pushed into the grain by the sanding movement.

Not sure that it matters hugely what sort of material you use to remove the waste slurry when you’re done.  As long as you get it off the top of the body whilst leaving it in the grain.  Your idea of a plastic card sounds interesting, swiped with the grain though, rather than across it.

All comes down to trial and error really.  Find a method that works for you in creating the finish that you want.  Different people have different approaches that they’ve finessed through practice and time.

?


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simon1138
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02/09/2020 2:54 pm  

after looking at the boiled linseed oil, it is still damp and the grain still there, as in not filled. it seems to sink, the thing with this method is it will take time to apply, dry off, then sand. i dont want to see the wood as i will be painting over it. are there other methods at all. i am thinking about rustins grain filler but its getting the mix right. i have the waterbased wood filler but that sinks as well. so either way its multiple coats.


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darrenking
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02/09/2020 6:23 pm  

Hi Simon,

According to the interweb:

Boiled linseed oil in thin coats dries in a few days and can be put into moderate service. Boiled linseed oil does in thicker applications does not fully cure or harden (dry all the way through) for 30-45 days.

So you may be in for a bit of a wait! Have you finished the neck yet? Just a suggestion.

For a smooth paint finish guitar you have picked probably the worst wood in the world for the body with ash being the next front runner in terms of being a bugger to get smooth and flat. The other option I can think of would be use either epoxy or UF resin almost like a body filler and then sand it back smooth once its cured. It going to take a bit of time but it sounds like you are discovering that already! Alternatively you could just learn to love the grain showing through the paint. Kind of cool IMHO.

I remember having to apply (raw) linseed oil to a new cricket bat when I was a kid, it took sodding weeks!. I think the season was pretty much over by the time I was allowed to play with it and the following year it was too bloody small for me!! Grrrrr!


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John L (Boo)
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02/09/2020 9:03 pm  

I would use Rustins or Aquacoat. What is the reason you don’t want to use them? Ok Aquacoat is expensive but it’s good and ok Rustins you may have to re-apply that’s fine. 

When I worked as a vehicle refinisher, when using car body filler, we used several coats to build up the correct shape. After that we filled the tiny holes, scratches and surface imperfections with stopper (an ultra fine filler). After that we covered it with high build 2k primer paint, this is effectively liquid filler. This would, when cured, be sanded down smooth to 800 grade and would then be ready to accept a colour base coat and finally top coat (clear coat). There are no short cuts, no cutting corners IF you want the end product to look amazing! 

Apply, sand, apply, sand, apply, sand........ 

 

Sorry, I don’t mean to sound like an “@rse” but it’s just the process. Keep going man! Rock n Roll 

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