what type of investment material should I use

Discussion in 'Investment casting Block method' started by Bill W, Jul 15, 2021.

  1. Tobho Mott

    Tobho Mott Administrator Staff Member Banner Member

    I'm not a lost wax guy. But I did post Bill Jurgenson's recipe and burnout instructions here FWIW: http://forums.thehomefoundry.org/index.php?threads/stacked-plaster-mold.1517/#post-34440

    He used this for 40 years in his art foundry. It worked well for him. But I have no idea how well it might work for vacuum assisted or centrifugal casting (often used to help molds fill properly when casting small parts). Maybe a taller mold with more head pressure could be used instead? From what Inhave read it may come with a bit more of a learning curve than using premix. Many who cast small parts do seem to find the consistent quality and detailed burnout instructions of premixed investment worth paying a little more for.

  2. Jason

    Jason Gold

    Ever hear, which came first the chicken or the egg? Now tell me where to get ludo.... o_O
    Tobho Mott likes this.
  3. Tobho Mott

    Tobho Mott Administrator Staff Member Banner Member

    That's where the 'virgin mix' part of the recipe comes in (not gonna ask what you thought that meant). After that, you have your ludo (crushed used mold material) for the next bunch of molds.

  4. DavidF

    DavidF Administrator Staff Member Banner Member

    You know, I googled ludo awile back and just came up with some rock band. Why not call it "used crushed investment" ??
  5. crazyjoe86

    crazyjoe86 Lead

    I've used R and R Ultra and Astrovest and Kerr satin cast ... the stuff I make is just as good...same with the ceramic shell slurry I make...used the R and R and the shellspen stuff...it's ain't only that it's cheap..it's more convenient for me to make what i need as I go...and not worry about ordering it and waiting...I go thru alot of investment...
    The Desert Yeti likes this.
  6. measuretwice

    measuretwice Copper

    older thread, but its prompted a question...

    Reading R&R's site, they state that resins expand during burn out which can damage the mold. Perhaps that is part of my problem, so I have been thinking of buying some of their Plasticast. However some print medium (like Anycubic dentalcast, or Polycast filament) call for some fairly high burn out temperatures. e.g. Anycubic suggests 900C. Does Plasticast cope with higher burnout temperatures than regular, say Ultravest, investment? Or is its advantage really just around addressing the resin expansion pressures?

    I also have a filament printed item using polycast (it printed beautifully!) ready to go and notice it also suggests some very high burn out temperatures. Its my understanding that investment for wax starts to break down over 1500F, so what to use for these high temperature needing print mediums?

    thanks for any help and advice.

  7. 0maha

    0maha Silver

    My experience with R&R has been that they are very, very helpful when you have technical questions. I'd send them an email and see what they say.
    Jason likes this.
  8. measuretwice

    measuretwice Copper

    Good idea. I had sent them a note re the Ultra Vest and they've just responded that its good up to 800C/1472F. Also asked about Plastivest, i'll report back when I hear.

    I've been trying with two resisn, Anycubic Dentalcast and Siraya's castable resin. While specifically intended for investment castings, both are at the lower end of the prince ranges for castable resin. I get fantastic prints with the Anycubic, but can't get a good burn out (mfg suggest 950C!). Siraya burns out well, but is a bear to print. Lots of distortion and incomplete prints as seems quite weak and pliable and easily breaks away from supports. Finally got some success using PTFE on the film, but its still doesn't print as distortion free as the Anycubic.

    Trials and tribulations.
    Last edited: Aug 8, 2022
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  9. bill

    bill Silver

    Recently I have been working with Liqcreate, a resin company from the Netherlands. I did a use case study outlining my process casting bronze, using their wax castable resin. It will show results you can expect to achieve. It may help answer some of your questions and of coarse I will be happy to help as well.

    The link below will take you to the testimonial.


    Hope this helps
  10. measuretwice

    measuretwice Copper

    Hi Bill,

    Your stuff looks great! Very impressive.

    Sorry for delayed response, I did find a Canadian distributor for that resin but they are out of stock. It still feels expensive for an amateur, but maybe that is the price of admission. I'm getting pretty good prints with the Siraya material using the PTFE on the tank film. The casting I tried was I guess a fail but doing some tumbling knocked the worst of the 'barbs' off so I may use it. The fail was in the finish. R&R told me their Ultravest is good up to 1450 and I corresponded with Optima people who said the same. A chap at Geeswein said all gypsum based material has the same limit so its either that or move up to very expensive high temp stuff (10/lb in Canada so that's not happening)

    The poor finish may well stem from the the resin expanding and putting pressure on the investment as you note in that link. I did an experiment trying to burn up a piece just sitting in the oven; unlike wax it does not melt so the expansion/pressure thing makes sense. I just bought a box of R&R plasticast that is suppose to solve this....we'll see how that goes next.

    Here's the lousy finish pulley I did. I'd just buy the darn thing but you can't get this size with the a large enough collar that will still fit as set screw (I suppose they all are for smaller shafts so have smaller collars). Also shown is the pattern so you can see what it started with. Typical burn out cycle but taken up 1450, 750F at the pour, AL @ 1355F.



  11. bill

    bill Silver

    Sorry can't really help with Aluminum casting. I have done so little casting with aluminum to have a helpful opinion. But what I can see is the resin appears to have a matte finish, according to the manufacturers instructions. Though in the photo there are some shiny areas. This may only be the lighting in the room. The cleaning and curing process for this resin is fairly strict and should be used as close as possible to the instructions. With all that said it seems the resin is printing nicely. The investment used for this casting is also working well. Looking at the casting I can see striations or layer lines and these would not be present if the investment or the process was faulty. I can see some chips on the one side of the model (most likely from supports) so these I will ignore. If I were to give you my best guess I would say porosity is the cause of the surface defects. The small holes may be inclusions, but I think they could also be caused by porosity from escaping gases.

    Hope this helps.
  12. mytwhyt

    mytwhyt Silver

    It may be that your flask temperature is too hot.. I think I read somewhere that Kelly said, flask temps over 500*f can be problematic. maybe not an exact quote.. Myself, I've had better results with room temperature flasks.. When you look at Kelly's foam and drywall mud castings, the metal is cast into what amounts to a room temperature mold.. The castings are almost always high-quality castings..
  13. measuretwice

    measuretwice Copper

    Hi Bill,

    This will be long, but I'm trying to convey all the info

    The Siraya cast (purple resin above) instructions are a bit of nightmare. They have instructions on their web site but they don't match a couple those of some youtuber's suggestions to who were it seems provide with different instructions that on Siraya's site - like a hot and cold rinse after curing. That is a bit frustrating and usually no reason is given so it sometimes feels a bit like howling at the moon.

    This resin is high maintenance! Just to give a sense of....it was very challenging to get a decent print with distortion


    or it breaks during the print (frequent issue)


    I built a "environmental chamber", some foam board, a heater and a thermostat to keep things at their recomended printing temps. I'd set it up and run it a few hours before printing to get the temp right. The resin still in the bottle was in the chamber, done this way so it was at temperature and could be shaken just prior to printing. The temperature was maintained throughout the print.


    After a dozen tries, with their recommendations about useless (exposures time just didn't work and lead to large distortions). I started to get good prints. Most times though they'd break. I found putting some PTFE on the FET worked, major problem being (I think) too much adhesion to the FEP.

    After printing, the challenges continue. Very short exposure to the alcohol or you get big white spots on it, and their directions say to avoid prolonged exposure. Then you have to cure in a bowl of glycerine vs air so my curing station wouldn't. Wall mounted a strong UV light and bought a turntable as well as mirror finish bowls to hold the part and glycerine.

    The shiny bits may have been a bit of resin, it is all hard to get it all and its not as visible when wet....plus I'm trying to minimize exposure to the IPA. As as a sidebar, I wonder why it would matter - i.e., it should be cured after the UV exposure shouldn't it?

    I'm trying my best to follow the manufacturers recommendations but it is not at all easy with lots of ambiguity, failures following the script and solutions that do work (like the PTFE) never mentioned by them.

    I was more the glass is half empty, but I certainly do not have your experience. The striations are visible on a lot of the surface but my assumption was the investment was not holding up for much of the surface, hence the rough finish.

    Something is going on, but as I've had great castings with AL and wax filament (print2cast), it suggests the issue is related to the the pattern material (Siraya) and how well it works with the investment. Here's an AL casting from a waxy filament pattern. While the finish is rough (because the pattern was rough), its extremely detailed and follows the pattern almost perfectly. It was done with the same R&R Ultravest and burn out cycle


    Maybe, but that doesn't fit the quality of the dog I got using the same pattern material and burn out/casting process. I thought porosity issues were more a thing with a combustion furnace not an electric one. I'm using 6061 drops (not beer cans lol). I'm not very experience casting, just trying to piece the story together.

    The Ultravest using in both castings above is at least 15 years old . I had an industry insider tell me despite manufacturers shelf life suggestions of 12 months, he claimed that while it is hydroscopic, it would last indefinitely if kept dry. With a diminishing list of things to try, I start thinking....maybe the investment is too old? That plus reading that resin burnouts expand, putting pressure on the mold made pick up a box of R&R Platicast. I followed all directions to letter, 2hours after pouring the investment it went to a preheated furnace, etc. And another fail.

    A horrible finish and a lot of flash indicating the investment cracked. Frustrating the that new recommended material cracked but the 15 year old stuff didn't. I'm at a bit of a loss at this point, maybe the sprue? I intentionally narrowed it at the casting thinking it would make for less clean up. I know that would wrong for gravity pour, could it be the issue with a vacuum poor? Still doesn't explain the investment cracking.

    Any suggestions welcome!


    Last edited: Sep 13, 2022
  14. measuretwice

    measuretwice Copper

    Hi Fredo,

    It might be worth a try as nothing else is working. However I did get a good casting in AL with the identical investment and burn out process/temps before (dog above) and for other metals even high temps have worked well.
  15. Respect for old thread
    Any updates .. was the difficulties solved?

    heaps of info already in thread

    I’m trying decide between filament or resin printing for small model engine parts
  16. I've done quite a few investment casting using both PLA and resin. Only a few were larger than 3" x 3" x 3". Both work, but the resin gave me considerably more detailed castings so I gave away my filament printer. I've posted a few photos of my efforts here in the past. The photo at the left was done using Siraya Tech Cast purple. I had previously used about five different types of resin and none of the others worked better for me and some worked worse. Cast has the best price and was most readily available. Investment was SRS Classic. I've had good luck with it, but except for Kerr Satin Cast I haven't tried any others because most suppliers won't ship to Alaska. Material was silicon bronze.

    Click on the photo at the left to expand it. Each steam valve stem U joint is made from three castings. Although the surface looks a bit rough, keep in mind that the smallest piece isn't much bigger than a grain of rice. These were made for a 1/8 scale live steam model, but I've successfully done this same part using the same supplies at six times the size and there are examples of them currently being used on three full-sized locomotives.

    I haven't tried any of the newer resins. Since Cast is working for me I'll stick with the devil I know.

    In response to the old question about how long investment will last, in my first investment casting done 3-4 years ago my investment was from a 50 (?) pound barrel of Kerr Satin Cast that was about 35 years old. I can't honestly say that fresh Satin Cast or fresh SRS investment worked any better than the old stuff. My stash of old investment didn't receive any special handling while stored, it was in a plastic bag in the barrel sealed with a tie wrap. It was probably beneficial that our humidity here is usually fairly low and it was kept at room temperature and never allowed to freeze.

    Also responding to earlier comments, I haven't cast any aluminum using investment casting, but have done quite a bit of aluminum casting using Petrobond sand. My understanding is that the flask temperature should be based on the melting temperature of the metal being cast, so for aluminum should be at a lower temperature than is used for bronze.

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