sandpaper saving tips

Hi everyone.

As I am now in semi production I am not ashamed to admit that Im trying to cut costs. Not in building materials but in the waste and dispensable things such as brushes sandpaper etc

My biggest fustration at the moment is using so much sandpaper in hotcoat sanding. Yes I am using enough surfacing agent and Im not overworking the hotcoat - no tackyness. But while sanding I keep getting gummies on the sandpaper which means that they end up in the bin quicker than I’d like. Sandpaper isnt getting any cheaper and using sanding discs doesn’t work out much more expensive than glueing sheets of sandpaper to foam pads (time and cost of adhesive ) Its not a huge problem but its certainly slowing me down a bit (I know cost wise its only a few dollars we are talking about) Im no tree hugger but I do think that from an environmental point of view I should be trying to minimize how much goes in the garbage.

Does anyone have any tips on keeping sandpaper useful for longer? Or other production tips that can reduce waste and perhaps save a few dollars?

Powder build up yes but IME shouldn’t be any gummy spots sanding hot coat. While still on the pad I have at it with a powerful shop vac with round bristle brush attached


" Yes I am using enough surfacing agent and Im not overworking the hotcoat - no tackyness. But while sanding I keep getting gummies on the sandpaper which means that they end up in the bin quicker than I’d like."

I think I must be doing something wrong with my hotcoats. I never used to have the sandpaper problem before changing premises, Due to not having access to UV I am now using mekp instead of UV Catalyst, and Im only kicking at 1% . Perhaps even though it doesn’t dry tacky there is too much styrene evaporation causing more gummies than what there usually should be. Next time I’ll try kicking at 1.8%

Yeah you are messing up somewhere if you don’t clip a box you can sand 2-3 boards with the same piece of paper top and bottom.

OP,  How long are you letting the hotcoat cure beore sanding?  Don’t think you can sand as soon as you would with uv cure.

Only two things will cause your paper to clog up on a hotcoat, assuming you use quality paper.

The hotcoat itself has the wrong ratio of catalyst or SA.


Your RPMs are too high and heat is causing the mess. The trick in sanding is: slow enough to keep the heat down, but fast enough to be efficient.

Also, rubbing the clogged sandpaper with sandpaper will often clear tbe clogging.

Thanks for the replies, yes, I’m doing something wrong somewhere with the hotcoat. Cure time is not an issue because I leave my boards a good couple of days before sanding so the boards are cured enough and not green. But still no tackyness to the touch a few hours after hotciating, I have been getting a slight orange peel appearance on some of my hotcoats, I think the answer must be there, my hotcoats are not particularly thick so I think the solution must be with kicking the resin faster. Since using mekp I have purposely kicked the resin a bit slower as I have seen some threads where people say that resin is slightly stronger when cured with lower catslyst ratios.

Using Rhynalox sandpaper saves $$$$. It last 3x longer than anything made in the US I’ve tried. 


If you have orange peel areas in a hotcoat, I can only guess that you’re brushing too much. Those areas are often the result of brushing the resin after it starts to kick. It disturbs the SA layer and actually does leave tacky spots, post cure. That will certainly gum up your paper, no matter how long you wait or what your sanding technique is. A slow kick is desirable in the lam resin for a bit of added strength. It allows the resin molecules to bind better and is less brittle. Hot coats don’t really need to be slow kick, since you’re going to sand away most of it, anyway. A good hotcoat will provide just enough of a layer to allow sanding the board out to a smooth, even finish. Too thick, and it it’s just wasted resin. Too thin, and you run the risk of sand thru. I always go for slow kick in the lam and fairly fast in the hotcoat.

The term “hot coat” implies that the resin was mixed fairly hot. Hence the name.

how does it compare to champagne? 

bammbamm turned me on to champagne but its expensive

I hear the paper from Japan and Norway ( I think fiberglass hawaiii/woodcraft sells it) is supposed to be good too

for me its usually speed

I know some people don;t like it but i think the combination of a heavy tool like the milwaukee and slow speed make a difference by letting the tool do the work instead of hand pressuring it. Probalem is controlling the beast and not having your back go out. Definitely good for popeye fore arms.

that why i like the mirca sanding screens, because you use very little pressure with those and you can wash and blow out the screens with soap and water to make them new again.

sanding epoxy is stil a bitch though always will be that’s why I got my festool rotex


I can’t paste in the direct link, maybe the above embedded link will work? It’s not exactly how I do it, they add in a fill coat prior to hotcoating, but looks like good methodology as a go by.

If you’ve got lumpy hot coat and your sandpaper is gummy, you’ve likely overbrushed and under catalyzed your resin. Set it off hot and spread the resin out lengthwise then cross-brush once then light lengthwise brushout from stringer to rails, each side. Catch excess drips with a stick or squeegee and walk away, you’re done.

Read this quote at least three times, then write it on the blackboard 20 times.     This is the definitive ‘‘how to’’ instruction.

This is how to prolong your sand paper. Nail or glue a square approx. ( 16"x16")  of carpet to the wall. When your paper begins to load up, (after atleast 2 boards), hit the carpet for a few seconds and this will clean and not dull your paper for continued use. You can also reuse your aluminum oxide resin coated sanding discs many, many times, by soaking in acetone and scrubbing with a wire brush. just my 2 cents. I’ve been doing this for 25 years.

Thanks for the YouTube link, I ended up watching a loadof hotcoat vivids.

Im definitely not over-brushing because Im aware of the potential problem with brushing too much, plus Im actually brushing the hotcoat less than the guys on the vids, however my hotcoats do seem to be on the thick side compared to what those guys are doing, I have always done the masking tape dam to get the hard edge but I saw one guy masking off the bottom if the board and then hotcoating the deck, this makes much more sense to me to get a hard edge without having to lay down a thicker hotcoat, I’ll also be kicking the resin faster.

Thanks for all your time, I think you have helped me figure out the problem, plus great tip with the carpet to keep the sandpaper alive longer.


It was a bad batch of wax in styrene causing the problems

…no such thing about bad SA…may be not the right amount of SA in the resin (too much sometimes) or not the right amount of paraffin in the styrene; so if the styrene evaporates too early you finish with a gummy hot coat.

Also if you put too much MEKP you finish with a rubbery and never fully cured coat.


-With some grits is not good to use them over and over again because they do not “bite” properly so you are wasting your time and burning the surface.

These are very handy…just put your sander disc up on the bench , pull the trigger , and clean the grit with the rubber belt cleaning stick…and they last a very long time.


You are right about the vast majority of everything you say, but in the case of there being no such thing as a bad batch of SA your a bit off the mark, the gumming up of paper only started with that batch of SA, I even did a test of the old batch of SA compared to the new-same resin and massive difference.
Maybe I got the last bit from a batch they mixed which didn’t contain enough wax.

Black swans didn’t exist until someone saw one.

I’ve had problems with SA before when the temperature has dropped. The wax in the styrene isn’t held in suspension and starts to solidify slightly. Doesn’t allow for proper mixing without heating up the SA prior to adding it to resin.