applying PVA over waxed mold surface ? It doesn't work  
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applying PVA over waxed mold surface ? It doesn't work - 11/10/2002 7:14:48 PM   
yclui


 

Posts: 43
Joined: 10/13/2002
From: Hongkong,
Status: offline 		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
       Post #: 1

applying PVA over waxed mold surface ? It doesn't work - 11/10/2002 8:17:25 PM   
SCALECRAFT


 

Posts: 1408
Joined: 1/7/2002
From: MONTEBELLO, CA, USA
Status: offline 		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

(in reply to yclui)
       Post #: 2

applying PVA over waxed mold surface ? It doesn't work - 11/10/2002 8:27:38 PM   
yclui


 

Posts: 43
Joined: 10/13/2002
From: Hongkong,
Status: offline 		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

(in reply to yclui)
       Post #: 3

applying PVA over waxed mold surface ? It doesn't work - 11/10/2002 9:11:12 PM   
peso


 

Posts: 99
Joined: 12/20/2001
From: Stockholm, SWEDEN
Status: offline 		I have had the same problem with PVA as you. Putting PVA on wax never worked for me. The wax brand was Meguiarīs 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

(in reply to yclui)
       Post #: 4

applying PVA over waxed mold surface ? It doesn't work - 11/10/2002 9:31:46 PM   
winship


 

Posts: 151
Joined: 3/18/2002
From: Plainfield, IN, USA
Status: offline 		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.

(in reply to yclui)
       Post #: 5

applying PVA over waxed mold surface ? It doesn't work - 11/10/2002 9:43:18 PM   
twinsRfun


 

Posts: 21
Joined: 9/24/2002
From: Western, IA, USA
Status: offline 		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.

(in reply to yclui)
       Post #: 6

applying PVA over waxed mold surface ? It doesn't work - 11/11/2002 12:24:17 AM   
boater


 

Posts: 89
Joined: 12/9/2001
From: Sacramento, CA, USA
Status: offline 		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.

_____________________________

Rudy

(in reply to yclui)
       Post #: 7

applying PVA over waxed mold surface ? It doesn't work - 11/11/2002 4:32:29 AM   
SCALECRAFT


 

Posts: 1408
Joined: 1/7/2002
From: MONTEBELLO, CA, USA
Status: offline 		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

(in reply to yclui)
       Post #: 8

applying PVA over waxed mold surface ? It doesn't work - 1/7/2003 9:52:28 AM   
ace2002


 

Posts: 73
Joined: 1/4/2003
From: petaluma, CA,
Status: offline 		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

(in reply to yclui)
       Post #: 9

applying PVA over waxed mold surface ? It doesn't work - 1/7/2003 7:03:06 PM   
winship


 

Posts: 151
Joined: 3/18/2002
From: Plainfield, IN, USA
Status: offline 		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

(in reply to yclui)
       Post #: 10

PVA - 1/7/2003 9:26:37 PM   
sayno2glo


 

Posts: 29
Joined: 1/2/2003
From: helsinki, FINLAND
Status: offline 		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

(in reply to yclui)
       Post #: 11

Submarines - 1/8/2003 8:53:42 PM   
CoosBayLumber


 

Posts: 2991
Joined: 1/20/2002
From: San Bernardino Calif
Status: offline 		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.

(in reply to yclui)
       Post #: 12

wax - 1/9/2003 6:33:56 AM   
boater


 

Posts: 89
Joined: 12/9/2001
From: Sacramento, CA, USA
Status: offline 		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.

_____________________________

Rudy

(in reply to yclui)
       Post #: 13

applying PVA over waxed mold surface ? It doesn't work - 1/11/2003 9:22:11 PM   
sayno2glo


 

Posts: 29
Joined: 1/2/2003
From: helsinki, FINLAND
Status: offline 		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.

(in reply to yclui)
       Post #: 14

applying PVA over waxed mold surface ? It doesn't work - 1/12/2003 9:33:11 AM   
CoosBayLumber


 

Posts: 2991
Joined: 1/20/2002
From: San Bernardino Calif
Status: offline 		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.

(in reply to yclui)
       Post #: 15

Wax - 1/12/2003 12:13:39 PM   
boater


 

Posts: 89
Joined: 12/9/2001
From: Sacramento, CA, USA
Status: offline 		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

_____________________________

Rudy

(in reply to yclui)