What is the Slickest Most Adhesion Resistant Prep for Sodium Silicate Core Boxes?

Discussion in 'Sand Casting' started by Melterskelter, Jun 20, 2021.

  1. Billy Elmore

    Billy Elmore Silver

    We use the Johnsons same as you have. Have always had good luck with it. They taught us to use at least three coats of wax when we are using it. The silicone spray works ok as well but when we had two different materials overlapping the wax seemed to do a better job of blending them together...probably has to do with the thickness of the coating we applied, but just could not seem to get things as smooth as wax would....especially imperfections we wanted to hide.
     
    Melterskelter likes this.
  2. Melterskelter

    Melterskelter Gold Banner Member

    Shellac fairs very very poorly with esther -cured SS. The SS seems to bond tenaciously to it.

    You are correct in saying I have used lacquer coated core boxes with good results. In some cases I have used the same box more than 50 times waxing it each time. One problem I unwittingly ran into was doing spot fixes to dings in the box
    and simply spraying those areas with shellac. Then I had adhesion issues in some areas. But, dimly, did not realize the difference in reactivity of shellac vs lacquer with esther-cured SS.

    I will be trying out the ketamine-epoxy spray paint very soon.

    I really think the background information regarding SS use is helpful. For me, I can see and feel results of mechanical and thermal processes. But, chemical processes are relatively hidden from view and can, therefore, seem mysterious.

    Denis
     
  3. Tobho Mott

    Tobho Mott Gold Banner Member

    Just make sure you turn the furnace off before you drink up and go relax in the sensory deprivation tank, Dr. Lilly! :confused:o_O
     
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  4. Melterskelter

    Melterskelter Gold Banner Member

    I was able to find Rustoleum brand aerosol epoxy at Tractor Supply of all places. But it is not carried by my rather comprehensive hardware store, nor Lowes, Home Depot, NAPA (they do have an epoxy primer), a generally very good paint store, or automotive paint supply house. I could find some at McMaster-Carr and there were one or two on Amazon. But the aerosols ship slowly on Amazon with an arrival in ten days or more.

    I did spray some Rustoleum epoxy onto a test piece of aluminum and it looks like it smooths out nicely and will provide a glossy finish. That sounds good. But, I am spoiled by
    lacquer as it dries in minutes and I can get two or three coats on in just an hour or so. It's been a few hours since I applied the epoxy and it is still tacky. The label says:

    "Dry and recoat times are based on 70ºF (21°C) and 50% relative humidity. Dries tack free in 2-4 hours and can be handled in 5-9 hours. Recoat within 30 minutes or after 1 week."

    Interesting that, contrary to most solvent-based paints, they want the surface of the first coat to be reactive and less than 30 minutes old or wait a full week and then recoat. Makes sanding between coats a somewhat lengthy process!

    This paint will be going onto the inner surface of the pattern I poured the other day as I hope it will make a non-reactive barrier to the Sodium Silicate (or maybe epoxy-bound) cores that I intend to make. I think I will try epoxy bonding to see if such a core will break down more with heat and be easier to remove.

    Anyone have any experience with epoxy-bound cores?

    Denis

    Added later 9PM: OK I had called HD locally and asked the counter person if they carried epoxy spray paint. I got a very authoritative and unequivocal "No." Well, now I rechecked the website and checked specifically on Rustoleum epoxy spray. The site says they have 23 cans! Brother!
     
    Last edited: Jun 24, 2021
  5. DavidF

    DavidF Administrator Staff Member Banner Member

    If you have a spray gun, I highly recommend using the evercoat 4:1 high build primer.
     
  6. Melterskelter

    Melterskelter Gold Banner Member

    I looked up the product you mention, David. It looks like good stuff and I suspect a paint you have a lot of experience with. I also understand you have have been painting cars etc for a long time.

    The only downside for me is using my spray gun to spray an ounce of paint on the small part I’ll be coating then spending 20 minutes cleaning up the spray gun.

    Denis
     
  7. DavidF

    DavidF Administrator Staff Member Banner Member

    It will save time over all. It's like spray bondo! It's catalyzed and sets up quick, sands easily without clogging up the paper.
    One coat can be sprayed to a thickness of 10 coats of rattle can stuff saving hours of work.
    So that 20 minute gun clean up is nothing compared to the overall time you save...
    Here's the water horse, now it's up to you...
     
  8. Melterskelter

    Melterskelter Gold Banner Member

    So you are suggesting that rather than being pig-headed I should use some horse sense and listen?:cool:

    Denis
     
  9. DavidF

    DavidF Administrator Staff Member Banner Member

    You can lead a horse to water, but you can't force him to drink....
     
  10. Melterskelter

    Melterskelter Gold Banner Member

    I drank the Kool-aid... Ordered from the local Autobody place. 1 gallon paint plus a quart of hardener will come to roughly 150 bucks.

    Denis
     
  11. DavidF

    DavidF Administrator Staff Member Banner Member

    You won't be disappointed...
     
  12. Chazza

    Chazza Silver

    Make sure about the safety requirements for using hardener Denis. Some hardeners are isocyanates and really bad for your lungs,

    Cheers C
     
  13. Melterskelter

    Melterskelter Gold Banner Member

    Last edited: Jun 25, 2021
  14. DavidF

    DavidF Administrator Staff Member Banner Member

    So it can...
    Cause you to go blind..
    Make your skin fall off..
    Make you throw up and shit yourself..
    And make you dizzy..

    Awesome!!! So much better than what I had been using.. :D
     
  15. Melterskelter

    Melterskelter Gold Banner Member

    Huh? The link I provided was for the Evercoat catalyst. Which CAN make you sick if you manage to eat it or have exposure to high levels. But, my point was the SDS for the Polyesters like Evercoat is much much more benign than the SDS for isocyanates. Maybe I am missing your meanig---"better than what you are using."

    Denis
     
  16. DavidF

    DavidF Administrator Staff Member Banner Member

    I used to spray alot of Imron and awl-grip.... great stuff, but terrible for you..
     
  17. Melterskelter

    Melterskelter Gold Banner Member

    In summary, I drank the Kool-aid and it was good!

    The gallon (probably 3 lifetime supplies for my rate of use) with catalyst came into the autobody supply today.

    I tried it out even thought I lacked the 2.2mm tip recommended for my JGA 502 siphon gun. I used the 1.5 which was on the gun. Even so it worked quite well in the gun and the paint does kick off and cures very quickly. Less than 2 hours after putting on 3 coats the paint sanded beautifully. And it does build without tending to run far better than anything I've used to date. I applied it to my in-progress aluminum pattern which I had pretty coarsely milled and did not make any attempt to get a milled slick finish. It was very easy to feel the cross-hatch pattern from the faccemill. After the coats of Evercoat and a quick application of 220 sand paper (which did not tend to load) the faces of the pattern were positively slick and smooth. Very nice product! The stuff sands like no other.

    I am anxious to put some epoxy over the primer, but will have to wait until the inside surfaces of the pattern are primed as well.

    Question for anyone who knows: where is a good place to buy a larger tip and needle for my JGA 502? Being pretty green at the spray gun aspect of things, I would appreciate a site that lays it all out with respect to what needle goes with what tip and which tips and needles fit which guns. So far I have not found that sort of source.

    Do they make a mini-cup for the gun as the 1 quart capacity cup seems way over-size for this application. Maybe I'll just attach a roughly 2 ounce fabricated cup to the siphon tube of my gun.

    Denis
     
    Last edited: Jun 29, 2021
  18. DavidF

    DavidF Administrator Staff Member Banner Member

    Just back your fluid control way out and drop your fan down to a 1/4 of its full pattern.
    This stuff goes on heavy like spraying undercoating.. I'm glad you like it. So is that 20 minute gun clean up time worth it?? Lol.
     
  19. Melterskelter

    Melterskelter Gold Banner Member

    I’ll just stay with the tip I have and reduce the fan as you suggest.

    The time saved in reduced sanding and filling compensates several times over for gun cleanup. Plus the way this stuff levels results in a smoother surface than I could get using conventional spray products. I am holding my breath to see how the epoxy goes on and how durable the combo will be in use.

    I have decided to put together a very small cup to attach to the siphon of my gun. If I were going to do a lot of spraying, I think a small gravity gun might be better. But the Devilbiss JGA is a good basic gun. I’ll just adapt it to the task. I’ll be using only an ounce or two of primer at a time and more than that fails to siphon in the qt cup I have. Even an 8-ounce cup which Devilbiss makes seems overly large.

    Denis
     
  20. DavidF

    DavidF Administrator Staff Member Banner Member

    You could just go to harbor freight and buy one of their gravity fed guns. It's just primer after all, no need for an expensive gun...
     

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