Heads up: Barnes 4PU Polyurethane NEW FORMULA

[mangozac]

Johncast; yes it is very frustrating! I firmly believe that the properties of the new resin are different enough that they should have renamed it as a new product rather than retain the 4PU name. If you want to check it out I suggest just buying the small 500g sample kit for your own evaluation.

From some brief browsing none of the other Barnes resin products have properties exactly what I'm after. I've bought the 860g Smooth Cast 305 kit from Back 2 Base-ix and I'll post the results as soon as it arrives.

SSB; Yes, the power usage of having to heat the moulds is definitely a concern. I know it wouldn't be massive amounts of power, but it's still just a lot of playing around. Plus I would not want to leave the heater going while I'm not at home and I don't want to have to hang around for hours while it post cures. Indeed the Smooth cast shouldn't be as sensitive as the Task 8.

[johncast]

Hi All

Have now used the NEW fomula 4PU looks like we have to make friends all over again. Not impressed.

I will do more casting this week but only expect to cast 2 to 3 castings of each item in a day. Items are very soft after 2 hours. Thin items are a joke.

With such looooonnnnnnggggggggg working time I can vacuum 10 items at a time and not have to rush. this is one bonus, and through the week I might find another.

Whos brain stuss was it to change the 4pu

johncast

Johncast

[mangozac]

John apparently the reason they changed the 4PU is because the old one jumped massively in price (and they always had supply issues with it). So it is understandable that they went with another product but like I said the new product is sufficiently different that they should have given it a completely new name.

Yes, of course the longer pot life is great, but not at the expense of such long cure times.

My Smooth Cast 305 arrived but I haven't had a chance to try it out yet - things have been pretty busy of late and not leaving a lot of time for casting. Meeting a lovely lady hasn't helped either

[johncast]

Hi All

Have been using this NEW 4PU resin for a week now and I am not making friends with it at all . The viscosity is different which is a positive I gess and all stays this way for some time in the mould and allows good time to vacuum. Then we have to wait for it to set ,and wait , and wait and wait, ...... and wait 2 or 3 hours later a solid item can be removed from the mould , any item with fine detail or is long and thin , difficult to remove from the mould as it is still soft and once removed the casting is like a soft chockolate bar on a hot day. 3 days later the casting is close to resemberling the old 4 PU .

Will purchase some easy cast or something as this change in the resin of 4PU just doesen't work for me.

Johncast

[mangozac]

OK well as per Alan's (Deadmeat's) suggestion I tried out some Smooth Cast 305. It's got a 5 minute pot life and for fine models is demouldable in 45 mins to an hour. At first I was very impressed with it - the pot life is nice and long, demould time is great at 1 hour and it's got a nice, hard cured state.

So I jumped straight in and did a heap of casting. Then I found the problem.

This stuff chews up moulds like there's no tomorrow. If you forget to demould at 1 hour then even with a good coat of mould release it grips the silicone really well and is tearing quite badly. It just ripped up a relatively new mould. I can notice it hardening up the silicone on the moulds over the dozen or so casts I've done - it normally takes a lot longer than that!

So it's back to the drawing board.

Barnes has a product called TC-890 which sounds pretty good when reading the , however it's about 33% more expensive than the 4PU (the Smooth Cast 305 was a similar price to 4PU) and sounds like cure time might be up to 2 hours. If it's going to give my moulds a longer lifespan than it'll be worth while though. I might pick up a 500g pack on Saturday to try it out...

I did contemplate the Barnes Procast, but it's only got a hardness of Shore 65D (the same as the new 4PU), which I just don't think is enough. The TC-890 has a hardness of 80, which is quite high. Johncast do you have any comments about the hardness?

[johncast]

Hi Mangozac

Problems still arising out of this change in the 4PU. All things good and then someome has to change things. I went back the the Easy cast ,picked up a kg set a few week ago. i do have 6 to 7 KG lot of the 4PU still on hand but have been using it on the tunnel portal I make , it takes 80 grams of resin per cast and is quite thick so the resin can set for as long as it takes , around 2hrs in the mould then I turn it out and let it sit on the bench in the workshop for a few days to set up hard.

As for the hardness the 4pu certainly felt softer and the smaller parts just bent over , holding them in your hand even after a few days. waste of time the 4pu .

As for you getting only a few castings out of the mould , I expect you are placing the mould in the pressure chamber and this puts more resin in contact with more of the mould surface as i read in a post here on this forum, All made good sence to me as I have had a small mould here made of the Barns 4601 rubber only do 12 moulds or so because it was a mould I placed into the pressure chamber each time i cast it. 12 Castings and that was it , the next cast stuck so much i broke the casting getting it out . I think I was using a supercast resin at the time. 4601 Pink rubber can get 30 castings out in most cases.

Johncast

[mangozac]

I know, I still can't believe they changed it on us!

Yes, I am aware that pressure casting shortens the lifespan, however it seems to also have a big dependence on the resin product. I have always pressure cast so the expected number of pulls is relative to that. The old (and new for that matter) 4PU never gave me issues and I could get a nice long lifespan of 35+ pulls from my Pinkysil moulds.

How do you find the Easycast? What's the hardness of the finished parts like? As you say, even days later the new 4PU is far too soft but like I said in my last post, Easycast and 4PU are supposed to have the same hardness...

I reckon I'll just bite the bullet and pick up some Procast this weekend. Easycast's pot life is a little too short for me.

[mangozac]

I give up

I was in Barnes on Saturday talking resins and I walked away empty handed (well I did pick up some silicone). There simply isn't a product available to suit my needs. The TC-890 range I mentioned above turns out to be super thick - the viscosity is up over 300 (compared to <100 for everything else).

Smooth Cast 305 is physically perfect, but it chews moulds out so badly I won't be buying any more of it.

Dalchem's sounds physically appropriate, however who knows how it will treat the moulds. It's listed as having an 80°C curing temp, which sounds pretty high to me?

Which leaves me with finding out why the new formula 4PU is not hardening as it should. If I can sort that out I can deal with the long cure time (it's not like I cast a high volume that requires fast turnaround). If really necessary an oven can be used to speed things up post curing. And at least the long pot life means that a heap of moulds can be filled in one go.

[Deadmeat30]

Try changing the silicone? ive just been sent a sample of some Bluesil (formerly Rhodorsil) RTV 3325 to test out. see if that makes a difference.

[mangozac]

Changing silicones would then be another big headache. Pinkysil is one of the best products out there.

I'm looking at acquiring some from one of our RA friends in Germany who has a product he claims is perfect. We just need to see how expensive shipping is going to be to see if it's feasible.

[DemigodGames]

Hi guys, thanks for this info - its very helpful to someone here in Australia who is trying to ease themselves into proper resin casting.

I can chime in on the easy cast material - the work time is really low, I use it for drop casting on a vibration table that tends to get most of the bubbles out, that said you have under a minute to mix it and get it into the mould if you have any hope of getting a decent cast!

I have also tried procast in the past and found it to be ok, abet the mould life was less then what I was getting out of the easy cast, and I was only using it to cast model bases so I just went back to the easy cast. Now that im about to cast my own miniatures, im really looking seriously at what my options are - its a damn shame that we had a good product here in Oz and now its gone.

[mangozac]

Thanks for the comments and welcome to Resin Addict, DG!

Interesting that you say Procast was not ideal for mould lifespan. How much difference to say the Easy cast was it?

I feel like we need to petition Barnes to bring back the old 4PU. Even if they sold it under a different name! The new one could be still used by all the people who don't care, leaving the good stuff to the discerning casters out there

[DemigodGames]

Hi mangozac

Sorry for the horridly slow reply but ive been in full blown development mode on the launch of our range... alas im back to looking at/searching for resin options give there is now a lul in development whilst i wait for work to come back in to me.

So as for procast, i found i was getting 15+ pulls from a mould where i was getting 25(ish) from easy cast before i started to notice mould issues... ideally i would want 40+ pulls from a mould before i throw it if its to be finacially feasable to sell on to the end consumer. I will add though that the casts from procast did seem to be better but the price and moulding costs left me looking for other options.

[mangozac]

That's interesting. What silicone are you using? I've now been using Procast for a couple of months and after tweaking my process (a good deep vacuum as it's a bit thicker than 4PU) I'm very happy with it. I'm getting great lifespan from my Pinkysil moulds using Stoner 302 Rocket Release as my release spray. I haven't kept track of exactly how many pulls yet.

40+ pulls depends heavily on the part. Parts that don't have lots of fine, deep detail for the silicone to grab to will easily to 40 pulls. Otherwise 30 is a more realistic figure to base prices on.