Casting the B9 Resin

A lost wax capable resin tuned for 70 - 200 micron slice thickness
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behold3d
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Post#41 » Sun May 11, 2014 12:50 pm

I would.like to add that it would.Be a mistake to let the material reach the top and stop the evacuating process. You can either mix in a larger container or relax the vacuum by allowing pressure back in and then reapplying vacuum. Eventually the material Will break and when there is no more trapped air it will fall

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Post#42 » Sun May 11, 2014 1:10 pm

Thank you very much for your answerThat sounds very well to me. I will look for a larger container. when I mentioned that I stop the vacuum process I actually meant that I relaxed the vacuum area letting enter some air inside. After it goes down, we continue to vacuum again... Is this last wrong? I think the solution is to look for a bigger container as you mention.

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Post#43 » Sun May 11, 2014 1:40 pm

It's not wrong.as long you take it to the point where the material "breaks" and looks like it collapses without releasing the vacuum. Bigger container Will help you though.

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Post#44 » Sun May 11, 2014 1:40 pm

It's not wrong.as long you take it to the point where the material "breaks" and looks like it collapses without releasing the vacuum. Bigger container Will help you though.

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Post#45 » Sun May 11, 2014 1:53 pm

Thank you for your answer. I am now only concerned about correct timing on the vacuum process. As I have answered Robert-Howle, I have found this information here: https://www.asiga.com/forums/viewtopic.php?id=252

"Investment Properties and Mixing:
Many people talk about investment drying in 15 - 20 minutes but that is really called gloss-off. The surface may appear "dry" but I can assure you that every bit of water that you mixed in there is still there. I'm just assuming that you are following the instructions regarding the total work time of the investment. If you mix and vacuum the investment too long you will get bubbles on your castings. If you mix it for less time than is required you will get weak investment that will give you rough surface castings even on waxes. You can get lines that look like a snail crawled across your casting and that is the defect name, snail trails. Other things that can give you weak investment is using tap water to mix your investment. Tap water is often contaminated with a variety of chemicals that can adversely affect the strength of your investment mold. When I train casters all over the world, I demand DI water be used for all investing because you have to know and control your materials before you can trouble shoot your process. I also insist on the casters weighing the water and not measuring it in some graduated cylinder. Graduated cylinders accuracy varies and it’s hard to know by how much. You can calibrate your scales so it’s fairly easy to know that 1 ml = 1 gram so always weigh your water and be sure."

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Robert Howle
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Post#46 » Sun May 11, 2014 2:31 pm

Those "smail trails" are called water marks. Usually occurs when u don't mix long enough (minimum of 3 minutes). Remember this is a chemical reaction goiing on in the mixing bowl. U can help speed the process by using water that is very warm to the touch. All investment should stand to cure about 2 hrs before putting in the oven (maximum hardness). I have put it in the oven with wax in as little as 30 min., this is not recommended with resin casting.
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Post#47 » Sun May 11, 2014 2:39 pm

Follow the instruction. Pay attention to the details like pour the powder into the water. It seems petty but start by following the rules and then break them.

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Post#48 » Sun May 11, 2014 3:38 pm

Thank you Robert, Thank you Toby. I will pay attention to details... As a rapid conclusion I can conclude the following:

1) I will use a bigger mixing bowl.
2) Pour powder into water
3) I will stir for 3 minutes with a mixer (we ditn't used it anymore)
4) I will vacuum the mixing bowl for 60 seconds
5) Pour into the flask, then vacuum again for 60 seconds,
6) Give some vibration.

I think these were not not problems with my Burnout, since I didn't worked with resin but with wax... that is why I will not talk about "steam problems" with resins into the first stage of burnout causing problems with mold cavity as some have already talked about. I am assuming these are only investment problems. Once again, thanks to all, as soon as I cast again I will let you know what happened. Thank you again.

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Robert Howle
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Post#49 » Mon May 12, 2014 3:50 am

That 60 seconds is after the "boil" starts and in the case of the mixing bowl after the rinse and fall of the plaster.
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Post#50 » Mon May 12, 2014 4:04 am

If your investment has a recommended gloss off of 12 to 15 minutes, You should be done with the entire process by 9 to 9.5 minutes .
Less then 8 minutes and you will suffer various issues like snail trails and weaker investment.
Now, Another thing to think about is that the 9 minute time MUST be used up with Mixing time, Vacuum time, Pouring time and Vacuum time again. So, if you are only doing a few small flasks, the mix time will remain the same... the Vacuum time may need to be extended a little as the vacuum process will happen quicker with only a few small flasks and the pouring time takes much less time for a small flask versus many big flasks.
So, adjust accordingly . Other then that, The advice given by Robert and other people is spot on.

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Post#51 » Mon May 12, 2014 7:13 am

Thank you Robert. I will do it as you mention. Thank you Metal Caster. My flask are never small, we do cast about 40-60 pieces per flask... As I see, my main problem is with the Vacuum process mainly. http://www.ransom-randolph.com/html/casting_defects_causes.html#bubbles%20or%20nodules

I will take care of all the process accurately.

Thank you!

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Post#52 » Wed May 14, 2014 4:11 pm

Just a small update. Today I have made a sort of an "A&B test" for analyzing the bubbles into my pieces. I have used Plasticast in one flask and in other "normal" investment. I haven't placed any wax or plastic tree. Just plain investment in both flasks.

In both tests I have made the following:

1) I used an adecuate mixing bowl (I used the same bowl, but with less amount of investment).
2) Pour powder into water
3) I mixed for 3 minutes with a mixer. 1 minute at low speed, 2 minutes at high speed.
4) I placed uncer vacuum the mixing bowl for 60 seconds.
5) I poured into the flask, then vacuum again for 60 seconds,

I am not sure about the results, since nothing was casted, I just wanted to check in detail the investment process. Can you give me your comments? I am not sure, but I am becoming to think that my vacuum is too old that it is not working properly anymore.

First image is the flask with Plasticast. You can see bubbles arising in this upper side.
Second image is the flask with normal investment. You won't see bubbles.

Are these bubbles normal? It is important to mention that in the back side, the flask with Plasticast is smoother than the one with the normal investment... (I will post some other pictures below). At the end, I do not care if bubbles are only in the upper side, but I am not sure if these bubbles are also in the inside of the flask.
Image

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Post#53 » Wed May 14, 2014 4:13 pm

Sorry these are the pictures. Again, first flask is with Plasticast, second flask is with normal investment. Upper side picture.
Image
Image

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Post#54 » Wed May 14, 2014 4:16 pm

Now...

These are the pictures showing the lower side of the flask.

Notice that Plasticast flask (left) is smoother than the normal investment (right). Do you think it would cast OK? What do you think?
Image

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Robert Howle
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Post#55 » Thu May 15, 2014 4:42 am

Should have waited 2 hrs to remove the bases (after full cure) Hard to tell anything about those flask now.
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Post#56 » Thu May 15, 2014 8:34 am

looking at the investment you are pouring it looks "lumpy" it isn't smooth at all
You should check your investment mixture. it is important to mix the powdered investment after receiving it from shipping.
many years ago we used to order ours in 50 lb containers. we always mixed the powdered investment before we used it after receiving it from the shipper after we started having problems with our process. that cured it and we mixed it even after we had it because it would settle as we used it.
every time you dip into it to pull out investment the heavier silica falls down first.
First of all it is gypsum based powder and it's the silica that settles during shipping as it is heavier than the other ingredients, not to mention it probably has been sitting for awhile at the warehouse. It is imperative to pull the powder from the bottom up.
you can do this by rolling the container around or turn it upside down and shake it. But honestly it is best to us a large paddle to mix it in the container you can also use a long paint mixer in a drill to move the powder up and down. or it works well to just reach down into the bottom and pull up powder with your hands a bit messy but very affective.
It is extremely important to use masks!!
The investment is contained in the larger quantities in a plastic bag so you can pour it out into the old container, mix the new one easier bring the bottom to the top add back what you poured out and continue to mix it.
You generally have 9 minutes from mix to final vacuum. if you vacuum past the 9 minutes or if you see the mixture's boiling action is getting very slugish, Stop!
2.5 min. mixing 2.5 min vacuum in bowl 2.5 min vacuum in can. I know it only adds up to 7.5 min but the remainder of time is used up in the transferring of the bowl to the vacuum, pouring the investment into the cans and the time it takes for the vacuum to reach full vacuum wich should be 30 lbs.
those times are used as a guide from me to keep it moving part of the extra time is needed for the vacuum to reach full vacuum you watch the needle and when it stops moving your investment should be boiling.
if you bell jar is leaking it may look like it is boiling but it may not be enough. I use water on the bell jar's sealing area. I usde to use vasaline but that was so messy. with water if the is a leak you can see it and just put a little water in that area and it seals it right up. DO NOT RELEASE THE VACUUM once it has reach it's max vacuum.
you can by rubber rounds that fit over your cans the contain the spatter and overflow if you want.
After the first vacuum of the bowl if there are actual bubbles as you pour it you have problems. also it helps to pour the cans at an angle along to side of the cans and let the investment fill up from the bottom. don't pour it directly in the middle of the waxes or down the wax tree.
vibrating is imperative during both vacuum of bowl and cans it need to be a lot more than you think. I pound on my table like beating a drum very quickly. gave up on the hand held vibrator 25 yrs ago.
The spatter I get from my investment usually comes from the cans and it will sometimes with 3 ro 4 cans under the bell jar toss investment all over the inside of the bell jar.
But mostly I think you mixed investment you show being poured is too dry, and if your water temp. is to warm it will harden much more quickly in the bowl that could be what happened there as well. You need to use as cold of water you can the colder the better
I use and always have used satin cast 20. so this is all I knwo about. I have tried other investments but nothing has ever come close to it's flexibility.
I notice your investment is dirty as well it looks like you have all kinds of black specks all through it. Although it has nothing to do with bubbles it sure doesn't look good.
depending on where your at altitude can affect the process I am about 300 ft. above sea level so I get a good vacum and very little problems.
but if your in Denver you might need to make adjustments to the process and mix it a little wetter.
as for the bubbles I think your mixing is too thick from the picture I saw.
Oh by the way it is important to always add the powder to the water, I see you adding the water to the powder and that in itself is a no no.
Always rinse your bowel out first and just pour out the water leave it wet inside it will help brake the surface tension on the sides of the bowl.
I'm so far behind I think I'm First !!

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Post#57 » Thu May 15, 2014 3:13 pm

Thank you akgold... You have been so kind with that explanation. You really help. Thank you very much.

We haven't mixed it into the box itself, nevertheless, the manufacturer mentions it is not needed, but I will do it as you mention. One thing I can do is to vacuum longer... I only vacuumed 1 minute in the bowl and 1 minute in the can... so... I will add some more time as you mention. I am In Mexico City, the altitude is about 7942.91 feet. Are you saying that I have to increase water? I followed instructions about 38 parts of water per 100 of powder. I have changed the process, I now mix the powder into the water. Those black specks are from the bowl itself since we blend it with a mixer. It seems we have scratched a little bit the bowl.

Once again, thank you very much!

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Post#58 » Thu May 15, 2014 3:16 pm

Thank you also Robert. I didn't wait 2 hours. As I tell you, there is nothing inside of them, just plain investment.

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Robert Howle
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Post#59 » Thu May 15, 2014 6:46 pm

I understand that nothing was inside, but pulling it off before cure gives the plaster the grainy look. If cured we could see the consistency of the plaster. Any time u move the plaster after gloss over, and before curring is finished, it loses its fluid properties and pulls and stretches kind of like dried out clay. Just can't tell anything about your finished plaster from those photos because u disturbed the surface before it cured.
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Post#60 » Fri May 16, 2014 4:10 am

I now understand your point Robert. Thank you very much. I will make another test soon. This time I will leave 2 hours the bases. Also I will give more time for vacuum. I will let you know. Thank you again.

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