yclui

My Feedback: (1)

Hello everybody,

I have been told by many that the correct procedure to prepare the mold surface is to apply wax followed by PVA but so far all my attempts have been unsuccessful. The PVA just won't stick to the waxed surface but form seperate beads of liquids. I have tried to thicken the PVA but it didn't help. May I know what I might have done wrong ?

Any advices will be well appreciated.

Y C Lui

SCALECRAFT

My Feedback: (13)

Hi

My guess is that your using a silicone based was, as a result the PVA "fisheyes". Use" Partall "wax and all the problems are over.


Steve

yclui

My Feedback: (1)

Thanks Steve. Wax is just wax to me and I am not aware until now that there are different kinds. May I know whether "Partall" is a brandname or an ingredient of the wax ? I have just gone over all words printed on the can of wax that I have been using but there is no indication of it's ingredient. Is there anyway to tell whether I have brought the right wax ?

Thanks again,

Y C Lui
from Hongkong

peso

I have had the same problem with PVA as you. Putting PVA on wax never worked for me. The wax brand was Meguiar´s universal mold release wax. It is said to be good. But I think there was something wrong with the PVA. It was based on alcohol and maybe it had absorbed too much water. At least it behaved like that. At the end I had to clean the plug thoroughly and than only rely on PVA. But I would not recommend it. Much too risky.
/PO

winship

http://www.rexco-usa.com/part4.htm

Go to this site and use their products as they are intended to be used and you will have no problem.

twinsRfun

Are you putting a very light coat of PVA on? Try Mist VERY LIGHT (DRY) coat on, wait 10 min. then recoat with a normal layer.
What color is the PVA purple, or green? The purple drys slower.
Good luck PVA can be trying. YES wax is not wax.

boater

My Feedback: (2)

Partall is a brand name, you must use a wax compatible with PVA, I had the same problem till I bought the right wax. There may be others that work with PVA, but I know Partall does work.

SCALECRAFT

My Feedback: (13)

Hi

As one post mentioned, "partall" is a brand name. It will work with almost any PVA.

In my 9 yrs of composite fabrication I have never left PVA out of the molding steps. My parts have always released and never causes damage to my hard molds.

I guess its fear of damage to an expesive time consuming process, the parts and mold.

Steve

ace2002

I cant afford to put PVA on my molds. I make large race car bodys, from all kinds of materials, and the Gel-Coats are colors, and the bodys need no paint. These people I deal with everday want a car to look good and if the pva is on the molds the parts look like crap.. these people pay me $10,000 for there bodys and I want to get paid. Wax on Wax on Wax on
Mike

winship

http://winshipmodels.tripod.com/pva_mold_release.htm

This link above will describe the value of PVA

If the mold you are using has curred to 97% then the part you are making will cross link to the surface of the mold through the wax. The PVA provides the physical barrier to prevent this from happening untill the mold is seasoned. I have made high temperature prop molds without PVA and had no sticking problems with Freekote. Chemlease also makes a good variety of release products.

I agree that PVA is not for every application. I have stuck some molds and parts in the past when not using PVA though. Another thing to think about when making parts is how many parts will be pulled from a mold. I have had mold resin combinations work fine for twenty or thirty parts before the resin started to etch itself into the mold. The curring agent was TETA which is highly reactive. So what I am saying in my case is that things started to change when the part numbers went up. With composites the variables are unlimited and very tricky to deal with. That's why ace2002 said to call him on the phone since there are virtually unlimited combinations and variables. Gell time for part size, how much heat the part will see, structural properties, economic considerations etc.

Winship

sayno2glo

My Feedback: (2)

Hello! It's my first post here. My home base is E-zone.

But I have been doing composites for 7 years now and newer used PVA . I thought people stopped using that in 80's .
For wings and fuses I use Mequiar's mold release wax and it has never stuck any parts. For things like props etc. what don't need super shine finishing I use other stuff like release paste what is easyer to work with.

/Antti

CoosBayLumber

My Feedback: (1)

I had the same problem as Peso above mentioned, but about ten years ago when I was building model submarines. I rarely got a shiney finished product using either polyester resin or epoxied fiberglass.

The surface had four coats of rubbed in Meguirs mold release wax and polished to a shine. Then green Partall was sprayed on, but it just kept dusting onto the surface. I tried light coats, heavy coats, in the morning when it was cool, and in the afternoon when it was hot. The names all had representatives within minutes of here and in contacting Mequirs, Rexford, the fiberglass folks, they all blamed it on one another. It all boiled down to that a mirror finish could not be obtained unless there was a metal mould present. We had no problem in popping out the finished product, just the appearances of the finished product. Problems developed when the buildup of hand wax made the surface looks worse and worse.

As a last resort, we wound up applying 1-2 layers of Mequirs wax before each application, and no PVA. This slowed things down considerably. The surface of the models got smooth, but never shiney. And, we found it much simplier to just quickly do a 600 grit sanding of the surface of the finished product, then prime it for painting as submarines are not shiney anyway.


Wm.
What works in the product catalogues, seldom works in the home garage environment.

boater

My Feedback: (2)

Coos Bay,
I had the same problem you did, I used Meguire's mold release wax and the part I did released poorly, asked a friend he said to use PVA, well couldn't get the PVA to not bead up on the Meguire's. Asked him again what I was doing wrong, found Partall wax and -- problem solved!! Guess Meguire's has something in it (I assume silicone) that doesn't like the water/alcohol base of the PVA. Murphy's law at work again.

sayno2glo

My Feedback: (2)

I'm sure that Mequiar's don't have silicone.
Today I find out that Swedish top f3b pilots use goodold yellow Simoniz. Years back I used it too and it worked fine. Professionals don't use PVA.

CoosBayLumber

My Feedback: (1)

BOATER:

We have a large chain of stores in area called S & W Plastics. In general, they have NUMEROUS items, and most of them are somehow involved or manufactured by Hastings Plastics.

I took a look again this morning for as you mentioned. The noted PVA was there, as was the tubs of Meguirs. The only thing else by Rexford was some aerosol, spray on type release agent. Clerk was not aware of any tubs of wax offered by Rexford. They only reccomend the Meguirs rub on wax.


May have to check elsewhere, as I need to do a few A/C cowls in a month or so. Don't want that dusting to occur again.



Wm.

boater

My Feedback: (2)

The local plastics store in Nor-Cal is Tap plastics, they have a web site, you could order the Partall there if you can't find it local. Maybe look under surf board making materials?????? I put my PVA on with a foam brush. Not looking for a Pro job, will be priming and painting anyway. I don't think you are going to get a real shiney surface using PVA. I am certainly not a Pro. Have only done hand lay-up, trying to get everything together to do some vacuum work, got the pump and tank, needing a controller and a gauge and a few more fittings. I found an old freon tank makes a good tank (already had it). Rudy

CoosBayLumber

My Feedback: (1)

BOATER:

Am headed off to the Pasadena Hobby show this coming weekend. I know of a place close to there which has an even larger supply of goods. Hopefully I can then pick up a tub. Interesting, in that the Rex representative never mentioned a non-compatibility of makes.

I originally applied the PVA with a little air brush. That took too long and dusted. Then used an automotive "touch up" air gun and that dumped on too thick, but was semi-shiney. Found a freind who had some sort of a sign painter's gun that was a good step up in size from the air broush and it worked fine. Had to return it when he moved away, and never found a similar one except at several hundred dollars new. I used a artist's sable brush several times, but the bristles eventially splayed and got streaks. Haven't done much since then, but will be in about 1-2 months.


Wm.

Bruce Thompson

Guys, I know everyone has an opinion so here is mine. I own a composite shop and build race car parts full time. I too had trouble with PVA and quit using it. Then I stuck a few parts over a couple of years and figured it just came with the territory. I then started using it again on new molds mostly out of fear of cross-linking. I used $1.95/can Kit wax. I too had trouble applying it and found that 5 - 6 coats of pva with the first two so light you could hardly tell you applied any and then heavier coats after. The problem was it took ALL DAY to prep a mold. Then Dan Winship was over at my shop and suggested trying a different wax (Part-all). He proceeded to lay on a coat of PVA that was ready to use in less than 30 minutes. Now I PVA almost everything, ESPECIALLY when I want a gloss finish. Pva will give a high gloss on a 400 wet sanded surface. It won't hide the sanding marks but they will be glossy. Don't give up trying different application techniques. This stuff does work VERY well and as I wrote in another thread you WON"T stick a part with PVA/Wax combo. BTW I used a $26 touch-up gun and 90 - 120 psi

boater

My Feedback: (2)

Thanks Bruce, its nice to get imput from someone that has alot of experience! I use a 19.99 touch -up gun from Harbor Freight, but have found the foam brush is good enough for what I'm doin. I'm not a Pro and since I want to avoid any more learning curves, I'll just stick with the wax and PVA, hell I rarely pull more than a couple parts from a mold anyways. If I was doin gel coated boats for sale, I'd probably go the wax only route and use polyester gelcoat and vinylester resin. Never wanted to sell stuff cause I don't do things fast enough or good enough. Always marvelled at how some guys could build airplanes for money , part time. I'd make 50 cents an hour. Have you ever heard of resin infiltration molding?? Kind of a variation on the vacuum bagging route! Saw a video on the Speed Channel of a big boat maker doing it. Of course a big boat used polyester resin, don't remember if they used straight polyester or vinylester.

Bruce Thompson

Actually I am getting ready to experiment with vacuum in fusion. I am making a car body shell that takes a lot of time to roll out by hand(polyester open molded). I don't know what to expect. From the research I've done on it I have gotten suggestions/responses that covered the spectrum, some of them were quite adamant for and against it. So we'll see. I do know that boat builders are using it widely. I have been told that they are using a lot of vinyl-esters. The big pluses for them are obviously the labor savings but also the drastically reduced VOC emissions.

CoosBayLumber

My Feedback: (1)

BRUCE:

Never had problems with parts poping out when using the Rexford Part-all, it was just in the application and finished appearances.

I used to apply until the surface was overall green. Looks as though I ought to keep going until it looks over-all glossy now.

I have been using plaster of paris moulds over thin plastic plugs. The plugs made from vac-u-forms.



Wm.

boater

My Feedback: (2)

Bruce, hope when you get done with your experiment in infusion molding, you'll give us a recap. Hope you won't be ripping your hair out. Thanks again for your insights.

CoosBay, thanks for chatting, best o'luck with your molding, did you get some Part-all wax?? I could send ya some in a small container if you'll pop for the postage. Rudy

PlaneKrazee

My Feedback: (14)

I bought a fiberglass fuselage from Mick Reeves. It has all the panel lines and rivet detail. It was coated with pva when delivered. A simple wash revealed all the detail with a shiney surface with no pin holes.

Brian

goony

Hi Im goony(steve hammond) from peterborough in the UK
I helped to develop this system for a company cant say WHO back in 1988 with very good results in the end I could do it so fast u wouldnt believe it, obviusly it depends on the size of the mould but in this example it was to make a box to carry a battery lorry size, Do u yanks call them lorries? 18 wheelers u know wot I mean that size anyway, so imagine a battery that size looking sideways on cut it from corner to corner at 45 deg ONCE only, this leaves u with 2 triangles nice easy mould shape then double this so I could make 2 complete sets at a time now the best bit I could GO from releasing the moulds Gelling laying up and realising again in under 60seconds, By the way I never use PVA this is strictly for ametures If u want good results do it properly this means finishing the plugs with at least 1200 wetndry and polishing till u can see youre face in it then this polished surface will end up on youre mould then polish it again then give it 10 coats of release wax allowing it to dry inbetween and buff each one to a shine u will get good results if u follow this.

regards goony

Bruce Thompson

Goony, I agree with your advice on polishing molds in theory. But I make parts for the racing industry and when I'm doing developmental pieces where I make just a few copies the customer is never willing to pay for the labor to do this and rarely do I have the actual time available. Its not unusual to go from an idea to an actual part in 2-3 days. PVA allows me to take certain short cuts in the process, specifically in the area of surface gloss.