Hi, guys i’m having issue with applying PVA after having waxed and polished the surface, i can seem to get a smooth finish after applying the PVA. any techniques will be greatly appreciated. also should i be applying multiple coasts?
Regards,
Fidzani
It all depends how your mould is with how many coats. Typically I only apply one thin coat but on moulds that may require some extra release I may apply 2 but rarely more than that.
I used to apply with a hplv gun but thought it was a waste of time so I just wipe it on with a cotton ball. I wetsand and clear my parts anyways so slight imperfections aren’t an issue with wiping it on.
I like to wipe it on with a clean microfiber towel. I typically do 3 light layers to ensure full coverage. Under the right lighting you can see how your wiping technique changes the PVA application finish.
i use a clean brush and i do one thick layer.
the trick for a smooth finish is the warm weather (or room temperature), the higher temperature the quicker PVA dries out and you have a good surface
Try this. Wipe talk powder onto your surface before pva. Zero fish eyes.
One of my employees showed me this technique. He first dusts talk powder through a shaker. He than rubs it in all the details and blows off the rest. He then sprays pva kind of how one would spray clear coat. Beautiful results.
In general I do not recommend the use of PVA altogether.
Only when the surface is not compatible with the resin used, or the mould is really bad, I recommend to use PVA.
I have found that if you are going to use PVA, the trick is to get the coats applied very thinly. I use a microfiber cloth, wipe in one direction only for one very thin coat as the PVA will settle better as it dries. Then, one coat in the 90 degree direction. Again, very thin. You will still need to do finish work once the part is done. Also, I have found that if the Partall wax is used, the PVA likes it better. Don’t know why.
If its partall no2 then it contains no silicone. That is why it does not fish eye. If you are getting fisheye’s on your mould surface then you have a contaminant on the mould surface. I’m hearing it now. Of course he has, that is stating the obvious. We’re did it come from, did the polish you used on the mould contain silicone? If it did then eliminate all silicone based polishes out of your workshop not a great thing to have in an FRP workshop. Always use non silicone based polishes or compounds. Once you have contaminated your workshop with silicone it is very hard to remove from the environment you are working in.
The other is what waxes are you using? Most waxes have a content of silicone in them.
Meguiars MGH8, Formula 5, etc.
This isn’t a problem as long as you apply and remove properly. Some are easier to remove and others are harder. Try a few of them, so you can make the choice on what suits you best. Always allow waxes to dry on the surface prior to removal. Always, once you have removed the wax buff the surface by hand with a new rag or microfibre cloth to a shine. Always cycle your rags. Meaning, dispose of the used rags, and always cycle your rags between each coat. The rag you use to buff the surface to a shine, use on the next coat to remove the dried wax. Then this rag is disposed of and and then so on. What is not a bad idea, is to seal your mould prior to waxing with solvent based or water based sealer, then wax your moulds. You will find you wont have to apply as many labour intensive coats of wax. Eliminate contaminants from your air supply as well. Oil and water traps are essential if you are using air to blow down moulds or spraying.
By applying the wax properly and removing properly you eliminate wax build up. It is a painful exercise removing wax build up from mould surfaces, and even more difficult removing it from the part you have made from the mould that has the wax build up. Do not over wax as well. Herman is right, if you have done the prep work PVA’s are a band aid effect, not a solution.