How do I get 'smoother' filler?
Discussion
Just been mixing some small bits of filler and no matter how much I 'fold it in' when mixing (with the hardener), when I come to apply it, I get bubbles, low patches etc. Is there anything you can thin it with to get it a bit more runny (in effect). I've applied it fast, slow, in long quick sweeps, shorter sweeps etc - all no good. When I sand it down, I'm invariably left with three or four low bits and quite a few pinholes.
If you keep on mixing and mixing and trying to get it smoother, the stuff goes hard before your eyes (matron) ...
P38 is what I am using.
Ideas please!
If you keep on mixing and mixing and trying to get it smoother, the stuff goes hard before your eyes (matron) ...
P38 is what I am using.
Ideas please!
MikeyT said:
Just been mixing some small bits of filler and no matter how much I 'fold it in' when mixing (with the hardener), when I come to apply it, I get bubbles, low patches etc. Is there anything you can thin it with to get it a bit more runny (in effect). I've applied it fast, slow, in long quick sweeps, shorter sweeps etc - all no good. When I sand it down, I'm invariably left with three or four low bits and quite a few pinholes.
If you keep on mixing and mixing and trying to get it smoother, the stuff goes hard before your eyes (matron) ...
P38 is what I am using.
Ideas please!
What are you filling over? assume it's nothing where the filler is sinking etc?If you keep on mixing and mixing and trying to get it smoother, the stuff goes hard before your eyes (matron) ...
P38 is what I am using.
Ideas please!
I fold it all up very quickly, spread it while sort of compacting it down, get a chunk on the spreader / spatula / HMV loyalty card etc, start the 'sweep' and put some gentle consistent pressure on. Keep the angle of said spatula thingy fairly shallow and apply a little pressure as you're sweeping it.
you'll never get a perfectly smooth finish, the devil is in the detail after you've applied it and the time comes to sand it down.
Also what grit paper are you using to sand and are you sure you're using the right amount of hardner?
Mikey, first up, it's a bad idea to "fold" when you're mixing the hardener and filler. If you use any sort of folding or whipping action you'll trap air into the filler and create a nice solid sponge that is full of bubbles which look awful when you sand the hardened filler back.
Try instead just using the spreader to scrape along the mixing board to pick up the filler and hardener with several strokes, then spread it down again smoothly, and repeat until the paste is all one even colour.
As for low spots, filler contracts as it sets. The deeper the build in a particular place, the more it will sink, because it sinks a proportion of its depth, not a fixed amount. If you don't do this professionally, simplest thing is to work on the assumption that you will need at least two coats, one to rough out, and at least another one to fill where the first skim has sunk to create an acceptable profile.
As for roughness - filler is a coarse, rough product. For something that goes on buttery-smooth and sands back to a much finer surface, you need a stopper. The downsides are stopper is more expensive, and because it sets so dense, sanding it back is a lot more work, and shreds your abrasives quicker. Get your roughing out done with filler, and switch to stopper for the final surface if you're doing big rebuild work. Alternatively, a very high build primer should sort any roughness and minor profile issues in your filler work.
HTH
Tol
Try instead just using the spreader to scrape along the mixing board to pick up the filler and hardener with several strokes, then spread it down again smoothly, and repeat until the paste is all one even colour.
As for low spots, filler contracts as it sets. The deeper the build in a particular place, the more it will sink, because it sinks a proportion of its depth, not a fixed amount. If you don't do this professionally, simplest thing is to work on the assumption that you will need at least two coats, one to rough out, and at least another one to fill where the first skim has sunk to create an acceptable profile.
As for roughness - filler is a coarse, rough product. For something that goes on buttery-smooth and sands back to a much finer surface, you need a stopper. The downsides are stopper is more expensive, and because it sets so dense, sanding it back is a lot more work, and shreds your abrasives quicker. Get your roughing out done with filler, and switch to stopper for the final surface if you're doing big rebuild work. Alternatively, a very high build primer should sort any roughness and minor profile issues in your filler work.
HTH
Tol
Edited by Anatol on Tuesday 3rd June 06:53
HRG said:
Millfield usually have stopper in stock 
Got some now mate 
Thanks to all - yes, I supposed folding it over wasn't the best idea - picked it up from the wife from cake making ...
I'm strating off with 120, then a bit of 240/280 (whatever I can find on the floor), then 600, then 1200 - I do have some 2400 but this isn't the final block yet.
I started off not using enough hardener and after putting some on I came back the next day to find the b
d still soft! Had t chisel it all off - not pleasant.Edited by MikeyT on Tuesday 3rd June 22:55
Most fillers need about 2% hardener.
Judging 1/50th by eye is pretty difficult - the eye/brain isn't very good at it. It *is* pretty good at judging halves though - so take your filler mound, and cut it in half with the spreader for 50%, then cut one half again for 25%, then 12.5% then 6.25%, then 3%(approx), and then you have a good idea how much hardener you need to add for a mix that cures properly.
HTH
Tol
Judging 1/50th by eye is pretty difficult - the eye/brain isn't very good at it. It *is* pretty good at judging halves though - so take your filler mound, and cut it in half with the spreader for 50%, then cut one half again for 25%, then 12.5% then 6.25%, then 3%(approx), and then you have a good idea how much hardener you need to add for a mix that cures properly.
HTH
Tol
I'm strating off with 120, then a bit of 240/280 (whatever I can find on the floor), then 600, then 1200 - I do have some 2400 but this isn't the final block yet.
Sorry mate but you're going about this all wrong
Start with 80 grit...on a block...get the repair done and only switch to a finer grade ,240's, to remove the scratches from the 80's.Then you're ready for primer.Guide coat the primer then use 600's wet n dry to flat the primer...again with a block.
Sorry mate but you're going about this all wrong
Start with 80 grit...on a block...get the repair done and only switch to a finer grade ,240's, to remove the scratches from the 80's.Then you're ready for primer.Guide coat the primer then use 600's wet n dry to flat the primer...again with a block.
V8covin said:
I'm strating off with 120, then a bit of 240/280 (whatever I can find on the floor), then 600, then 1200 - I do have some 2400 but this isn't the final block yet.
Sorry mate but you're going about this all wrong
Start with 80 grit...on a block...get the repair done and only switch to a finer grade ,240's, to remove the scratches from the 80's.Then you're ready for primer.Guide coat the primer then use 600's wet n dry to flat the primer...again with a block.
It's all with a block. The 80 is too coarse I have found. The 120 works fine. Then the 240 etc. again works fine. Maybe I should be guide coating wit with the primer sooner rather than later though ...Sorry mate but you're going about this all wrong
Start with 80 grit...on a block...get the repair done and only switch to a finer grade ,240's, to remove the scratches from the 80's.Then you're ready for primer.Guide coat the primer then use 600's wet n dry to flat the primer...again with a block.
ff5317 said:
Use 80 to 100 on the filler, then use a filler/primer over it and stop up any visible lows with polyester, then guidecoat it and either da it with up to 240, or wet flat with up to 600. That is how we used to do it in a pro bodyshop.
same process I use, though I too use 120 at the start as opposed to 80 grit.MikeyT said:
I'm starting off with 120, then a bit of 240/280 (whatever I can find on the floor), then 600, then 1200 - I do have some 2400 but this isn't the final block yet....
I'd suggest the finest grade to finish off the filler should be 320, or maybe 400. Any finer and you can start getting problems with the primer not keying to it properly.As regards to hardener in the filler, 1-3% is the norm. If you use too much hardener, you'll start to get bleed through in the topcoat- basically, the pigment in the hardener will stain the paint, leaving a shadow the shape of the repair visible. As this is caused by the hardener, no amount of re-coating with paint will hide it, you'll either need to re-skim filler over the effected area (doesn't always work), or remove the filler & start again.
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