Marks on gelcoat

[Jonathan Muller]

Hello! After I removed the part from the mold, these marks always remain on the mold but also on the part removed from the mold. The waxing process was this. 6 coats of TR-104 wax because the molds were newly built and the next day before applying the gelcoat and lamination I applied another coat with an hour's drying time. What could these stains be?I'll leave some pictures below. Thanks

 

[tpenfield]

I don't have much to add, but following along with interest.

How 'new' are the molds? Did you buff the wax to a shine?

 

[Jonathan Muller]

I don't have much to add, but following along with interest.

How 'new' are the molds? Did you buff the wax to a shine?

Brand new.Yes I buffed them with a cotton rug.

 

[ondarvr]

On my phone it's a little difficult to see, but it looks like pigment separation. It's not uncommon if the balance of white and black is incorrect. The solution is to have the color adjusted to a lower the pigment loading.

 

[Jonathan Muller]

On my phone it's a little difficult to see, but it looks like pigment separation. It's not uncommon if the balance of white and black is incorrect. The solution is to have the color adjusted to a lower the pigment loading.

Hello! It's quite hard to see because of the gloss of the mold. The light is reflected and it's hard for me to take a clear picture. It looks as if some pieces of wax are coming off the mold and remaining on the piece.

 

[Jonathan Muller]

On my phone it's a little difficult to see, but it looks like pigment separation. It's not uncommon if the balance of white and black is incorrect. The solution is to have the color adjusted to a lower the pigment loading.

Can I send you photos on email or other type of comunication?

 

[ondarvr]

What is the actual color of the gel coat, it looks dark gray. Can you feel any texture on those areas?

 

[Jonathan Muller]

What is the actual color of the gel coat, it looks dark gray. Can you feel any texture on those areas?

the color is black! I don't feel a different texture, just a change in shade. Those areas seem to be more matte

 

[ondarvr]

If it's just a color change, then it's pigment related. What equipment are you spraying it with?

 

[Jonathan Muller]

If it's just a color change, then it's pigment related. What equipment are you spraying it with?

I'm spraying with a LVLP gun with 1.8 mm nozzle.I'm using clear spray gelcoat and I'm putting 1% pigment in it.But if I polish the mold with a sponge and polishing compound, these spots disappear.Couldn't these stains be caused by the wax being applied too thickly or not drying enough?

 

[ondarvr]

That size tip is small for gel coat, are you reducing the viscosity with something?

 

[Jonathan Muller]

That size tip is small for gel coat, are you reducing the viscosity with something?

I don't use any thinner! To get good coverage, I make several passes until I get a thickness of 450 microns. This is for the gelcoat of the parts. The mold gelcoat is applied with a brush in two layers with a total thickness of 1000 microns.

 

[wet feet]

That is a very low level of pigment.I also wonder about the evenness of the gelcoat layer,how are you able to verify the uniform thickness of it?How long are you leaving it before applying subsequent material?Was the mould made with tooling gelcoat and regardless of the answer to that,how many coats of gelcoat were used on the mould?Knowing more about these matters would be useful to understand what may have happened.

 

[Jonathan Muller]

Hello! The mold was built with vinylester gelcoat specifically for molds. It was applied in two layers with an interval between layers of 4 hours. The total thickness of the layer is around 1 mm and was measured with a thickness measurement card (gelcoat thickness gauge). The mold gelcoat was not pigmented but came directly pigmented with black from the manufacturer. These stains remained only on some molds and of course also on the piece that was removed from the mold.

That is a very low level of pigment.I also wonder about the evenness of the gelcoat layer,how are you able to verify the uniform thickness of it?How long are you leaving it before applying subsequent material?Was the mould made with tooling gelcoat and regardless of the answer to that,how many coats of gelcoat were used on the mould?Knowing more about these matters would be useful to understand what may have happened.

 

[wet feet]

I'm a bit confused here,the earlier mention of 1% pigment made me think that was what you had added to the gelcoat and it is a low figure.The blotchy areas of the mould may well be related to the wax build up and I'm not familiar with that particular wax in any case.What does the data sheet recommend for it's application?Things like workshop temperature and time before buffing can make a difference,as can location as the humidity level in a building next to a lake will be different to that in a region far from water.