I am having trouble with my finishing sanding. when i hold my boards up to the light i can see un-uniform scratch marks at different angles
this is my final sand where i am using 400 grit.
what techniques do you use for finish sanding?
hand sanding nose to tail to get perfect parallel lines?
small circular patterns so that there is no “scratch lines”
random orbital sander?
finish sander?
any help with the final final sand techniques you use would be awesome. I want my boards to have a sanded finish similar to how you see in the shops.
when I hold those boards upto the light you cant see any scratches.
is a nice sanded finish even possible without using an acrylic coat.
400 grit will show 400 grit scratches. 800 grit will show 800 grit scratches. 1200 grit will show 1200 grit scratches.
if you want a mirror finish use a mirror finish grade grit. for most a 400 grit is fine, but if you want a true plate glass finish, you are going to have to run the grits up a bit higher.
if Im doing a wall hanger mirror finish. zit take down with 220 or 320, then 400, 600, 800, 1200, …and a polish out with a very very fine polish…I’ve been know to take it out to 2000 grit if the color is black, dark blue, or deep purple.
its got nothing to do with the motion of circles, each step you need to take the scratches out from the previous grit…you are making smaller and smaller scratches. if you skip a step or miss an area, then you are just polishing scratches. Stopping at 400 will just give you some very shiny scratches. You need to remove the scratches…then polish it out.
Sanding an acrylic coat? Most acrylic surfboard coatings are not made to be fine sanded. they are speed finishes. Speed finishes will never polish out like a 2pac spray, or a poly gloss coat…even if you use a Krylon clear coat, the paint will only get so hard. Part of the trick is in the polish buff out…speed with a hard surface will make the finish pop. if you are using an acrylic soft finish, you will never be able to get that speed up…it will burn.
…Resinhead, the poster is asking about a sanded finish not a polished gloss finish.
-Sand the hot coat then apply a gloss coat then start to sand it with 320 then 320 and 400 by hand.
Other technique is to sand it up to 600 then sand with a coarser 3M sponge and a matte paste.
I’d say a lot of the ‘sanded’ finish boards do have an acrylic spray or wipe-on finish followed by a linear scuff pad sanding. A sanded board generally has too many areas of exposed weave for them to get away with just putting it on the retail floor. The acrylic finish makes the exposed weave disappear.
as everysurfer said all sand paper are not equal. i learn too from a car painter to keep no more than 100 between grit for dry sanding and 200 for wet. orbital sander with small orbit nod soft pad is normally made for finish.
I have heard that a 320-400 sanded finish is the fastest finish. Might want to consider this if speed is a priority. But i’m not sure how much of a difference it makes because I have never tested this personally. But there must be something to it because I have read/heard this from many sources.
JM and Resinhead are correct in both instances. Whether it be a “Sanded” finish with a wipe-on sealer or a Gloss Polyester; if you can’t live with scratches you will need to go to the next Grit. I like to do as the old guys did back in the day and finish off with water on Wet n Dry by hand. You can use the most expensive automotive polish available, but if you didn’t do a good thorough job of sanding thru the grits; you’ll just be polishing scratches. The wipe-on Acrylic Sealers can be “burnished” with a Maroon or Grey 3M pad under an Orbital Sander. This process levels the finish by heating it. It also makes the finish pop. Lowel
I like to watch TV shows about guys building cars. A lot of them will show how they do the sanding before painting. The use angled strokes for each grit and go in opposite directions. That way they can see if the previous grit has been worked out. They also use long blocks. They’re always talking about how critical the finish has to be prior to paint.
We can use those techniques for boards. I’ve done it for the boards I want to have a shiny finish. I’ll sand down to 3000. I do it outside and wash with running water after each grit.
I find that after dry sanding to 320, then wiping acrylic, I can then wet sand with a bucket of water using 400 then 600 and get a very shiny bottom. Be careful not to over-sand the acrylic or you are back to the resin underneath.
For shortboards I generally sand with the machine to 320 and then use a piece of 320 glued to a piece of mattress pad foam and hand sand with full length passes from nose to tail as the final step before putting on 4 thin coats of behr concrete sealer. I follow that up with a wool pad in the polisher. If there is color work I will wet sand to 600 just so the colors have a little more pop.
the first step is to be sanding flat otherwise you won’t be able to remove low spots or gouges.
My steps are
180 Medium Pad
180 Orbital
Tuck in the edge with orbital and sanding block, then hit the tight spots around the tip of the nose and rail with the sanding block.
240 soft pad the rails
180 hand sand rail
240 hand sand rail.
240 orbital the flat
240 orbital soft pad over the rails to blend the straight lines from hand sanding into orbital scratch.
Then I do one check over to look for shinys scratches etc.
Then 320 or 500 wet rub with an abralon pad on the air compressor orbital.
This is my standard finish on a board with one filler coat no gloss coat. If we ever bring up to much weave thats visible like on a dark coloured board well just clear spray it with a matting agent that acts like a gloss coat and can be rubbed back or straight scratched.