Hello all.  I have made a mould using the Uni-Mould system.  The pattern was finished with Pattern-Coat High-Gloss, and had some scratches (I had started with 80 grit).  But I made the mould anyway and the scratches, as expected came through.  So the scratches on the mould were now male scratches and easier to remove.  So this time I started with 400 grit wet (wet, circular motion, 3 sessions), followed by 800 (wet, circular motion, 2 sessions), followed by 1200 (wet, circular motion, 2 sessions).  Attempted polish with Topfinish2 and medium/soft blue pad in DeWalt polisher, but ended up with deep scratches.  Also have attempted NW1 cutting compound with medium/hard orange pad, still no cigar.

I have ordered 1500 and 200 grit, I will start again at 800 grit and go through 1200, 1500 then 2000. And then probably NW1.

Any other suggestions? You can clearly see the scratches in the pictures, the phone camera picks them up really well. In the third picture, you can see how rough the surface is in the light section. One problem is that the entire mould is concave, but my pads are flat.  Are there hemispherice pads available anywhere?

+x

 

Robert72 - 10/6/2019 1:20:50 PM

Hello all.  I have made a mould using the Uni-Mould system.  The pattern was finished with Pattern-Coat High-Gloss, and had some scratches (I had started with 80 grit).  But I made the mould anyway and the scratches, as expected came through.  So the scratches on the mould were now male scratches and easier to remove.  So this time I started with 400 grit wet (wet, circular motion, 3 sessions), followed by 800 (wet, circular motion, 2 sessions), followed by 1200 (wet, circular motion, 2 sessions).  Attempted polish with Topfinish2 and medium/soft blue pad in DeWalt polisher, but ended up with deep scratches.  Also have attempted NW1 cutting compound with medium/hard orange pad, still no cigar.

I have ordered 1500 and 200 grit, I will start again at 800 grit and go through 1200, 1500 then 2000. And then probably NW1.

Any other suggestions? You can clearly see the scratches in the pictures, the phone camera picks them up really well. In the third picture, you can see how rough the surface is in the light section. One problem is that the entire mould is concave, but my pads are flat.  Are there hemispherice pads available anywhere?

For those mould scratches, NW1 is the way to go.  Also you need to ideally be at 1500 grit or better. TopFinish is a medium to fine cut and as such 1200 grit is way too coarse for it to remove the scratches.  NW1 is recommended from 1200-1500 grit and upwards.  If you are picking up MORE scratches polishing then there is either grit in the pad or on the surface and/or your polishing technique is too aggressive.  For complex shapes like that, you can if you want, carve the pad or abrade the pad away to curve it to fit  - some softer pads with heavy wear end up like that naturally.  An alternative would be to move down to a smaller pad such as the 80mm version of our Medium/Hard (Orange) Polishing Pad which should be a lot easier to handle on that mould. 


Wayne, sorry to hear you are struggling so much with polishing the GlassCast 3. Something is definitely going wrong somewhere in the process.  We have a lot of customers successfully polishing the resin back to a high gloss, some with our polishes, some with other brands, so if everything goes right you should be able to get a good finish.  First thing is ensure the resin has had plenty of time to harden properly before sanding and polishing. NW1 is designed to work from 1500 grit upwards so 3000 grit should be plenty smooth enough. 

Sanding can sometimes take a lot longer than you think working through each grit to remove the scratches from the previous one.  You need to be very careful on avoiding transferring dirt or grit as you move finer through the papers, otherwise the grit will cause more scratches.  Also take care to avoid skipping grits or moving too soon to the next grit before you have fully removed the scratches from the previous grit. Once you are 100% confident you have got a minimum of 1500 grit evenly throughout, then you can move onto polishing.

NW1 is self lubricating so no need for water.  Also, it is easy to apply too much in one go.  As the polish is a diminishing abrasive, it starts coarse and gets finer, so if you have too much, you end up smoothing the surface initially then accidentally rubbing the unused excess polish back onto the part scratching it up again as you put coarse grit onto a partially polished surface.  Don't go too mad on the polishing speed and try not to work on too large an area in one hit.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

On top of what Warren said, be aware that 1200 grit is the real minimum for polishing, and as such it will actually take a long time to polish out completely. 1500 will polish faster, 2000 is fairly quick, and 3000 will polish out almost immediately. 

Wayne, it took me 5 years of doing this professionally to get to the point where I can wet sand and polish resins and gelcoats to a genuine mirror finish. It is not easy, it is a skilled technique, and it takes plenty of practice. Just keep with it, the products are good so you will get there eventually.

Hello.  I asked thepolishingshop.co.uk to see what they thought, and I got this reply all but a few minutes later:

"Process-

We have a few options here-

Wheel based finis then-

Important to sand to around 1500

Then

Stage 1 - Glosswax 16 with a G quality mops (coolair or standard construction)

Stage 2- P175 Black with a WDR quality mops (coolair or standard construction)

IMPORTANT- Run Coolairs slow ie 1000-3000 rpm max, standard mops can be run faster but would still recommend 1000-3000rpm max. Please dont run at angle grinder speed, mops are rates to only 3000rpm

Its a standard process for a gloss finish, good example are bath companies as they are often sanded down then polished with this method.

I do have a liquid gelcoat system that would work, it comes down to if you want to use Pad or Mop as I am sure we can get the results on both. I think looking at the shape mop/wheel based would be better.

Best Regards Andrew"

I will give this a bash this/next weekend and let you know how I get on.

Just be a little bit cautious with your product selection. Products containing wax will ultimately give a very good finish, but they are unsuitable for use with composite tooling because they contaminate the surface and affect the performance of release agents. I don't know the products mentioned above, it's just the name Glosswax that concerns me - it might be totally fine.

If you give it a go, just make sure you thoroughly clean your mould with a good quality mould cleaner (NOT acetone) after you are finished polishing. The mould should retain its gloss, if the gloss is removed by a mould cleaner then it is because the polish contained wax that provided an artificial gloss.

Hello, I have attempted the polishing with the mops, it seems to be working really well so far.  I will upload some pics to the thread when the mould is complete.  I am about to post a new question regarding the split lines (need to get them done before I call it a day with polishing).