Effect of environment on casting

[BeeMan]

This is a spin off from the 'Casting too hot/fast' thread. Maybe I've worked on too many structured problem solving projects at work lately, but this seems like an opportunity to define specific symptoms and separate the causes of each.
:roll:

Bear with the long post as I attempt to frame some discussion. You guys are the experts; I'm just trying to facilitate capturing some knowledge.

One poster commented that base bubbles are a pressure / fill rate issue. Several answers addressed temperature factors, including lead temp, mould temp, cooling rate, and resulting sprue hardness relative to core of the boolit at time of sprue cut. Some of these answers seem addressed more on the void left inside the sprue or immediately surrounding it.

I'll start by speaking to a pin hole in the base which is clearly separate from the sprue. That is the way I initially read xxclaro's description and it is what I recently had trouble with.

I'm thinking the fill rate/pressure explanation makes sense for explaining this condition. I'm actually looking at venting, which is a matter of relieving pressure. I'm also remembering several members say that casting is best when the air has condensing humidity. The first couple questions I have are:

What makes condensing humidity produce better boolits?

Is this a matter of rain being associated with lower barometric pressure and enhancing venting, or is the high humidity the more relevant factor?

Have fun - dinner is on the table and I'm going to eat.:Fire:

BeeMan

[Springfield]

I dunno nothin' about rain, but I find casting early on a cold morning is not conducive to making good bullets. For some reason I just can't get good fill-out and the bullets tend to stick in the mould more. Nice cool evenings are no problem.

[docone31]

I believe, environment is an issue.
A lot of casters live in the west, and northwest. Down here, humidity is high, but no rain. Comparable humidity elsewhere and the sky falls.
I have seen different days produce different results.

[stubshaft]

I don't cast in the rain.

[felix]

That has me puzzled too, BeeMan. Corky and I have discovered that more or less independently and approximately at the same time, say 8-10 years ago. Just by luck? The same conditions here is Fort Smith as in Tulsa those times? Prolly, because it does not happen that way normally, and we would therefore remember it. His location is windy and drier than here in Fort Smith, almost always.

Thinking about the conditions contemplated per this memo, and using previously gained knowledge with powder and gasoline seperately, and how they operate, I have to conclude that it has to do with the transfer of heat, or better yet, the minute transients which are involved. This would imply a true condensing condition making casting best in the evening right when the sun is going down on a strongly evaporative day. However, I have done some excellent work during the morning hours as well when the pressure is rising after a rain the night before. Corky, on the other hand has has consistently very good results during a rain in his open garage. The only common key is the application of water vapor.

Keep in mind water injection systems for gasoline tend to cool the mixture, thus having the effect of dramatically raising the octane. Some other folks say the added moisture causes more compression, and even others say the added expansion is responsible when the cylinder fires. I have never heard a ping during a condensing atmosphere when normally there is one at high noon on a cold day. So, it cannot be ambient heat, but some kind of gradient.

Powder looses moisture over time in cardboard containers in low humidity environs. The powder becomes a notch faster in ignition, and at the same time will flatten primers in marginal loads because of the change in total speed. More energy? Nope, powder the same (volume measured).

Some labs will have to get involved in this to prove anything. All we can say at this point, keep some water around when casting. One way or another.

... felix

[arcticbreeze]

What makes condensing humidity produce better boolits?

Is this a matter of rain being associated with lower barometric pressure and enhancing venting, or is the high humidity the more relevant factor?



I can't actually answer the question but what I do know is pressure effecting casting may be coincidental to rain. What I mean is it might be that barometric pressure affects it and it so happens that this often occurs as a front with cooling temps roll in. In turn the same thing that allows better casting often facilitates rain. Precipitation or condensing humidity IE rain or dew is purely a function of temperature dropping below dew point. So I would be curious if a falling barometer is the actual condition allowing for better casting because I don't think moisture is.

[454PB]

Since I'm the guy that suggested it's a pressure/flow rate problem, I have to say it happens at any temperature or humidity level. Also, I think it is a venting problem in the sense that the cavity fills so fast that air bubbles get trapped between the boolit base and the sprue plate.

What I don't know is why it only happens with my Lee moulds. Perhaps they just don't have sufficient block venting.

Back when I was still lubing my Lee moulds, it was much worse. The lube contaminates the mould block surfaces, turns to a dark brown coating, and plugs the vent lines.

I quite lubing Lee moulds years ago.

[BeeMan]

Good input, all. I've got some thinking to do, and if I can figure out how to control some variables, some tests to design and run. Ultimately, I need to cast enough consistent boolits for a match one week from Saturday.

BeeMan

[mooman76]

Rain? Humidity? What's that?

[Slow Elk 45/70]

Me, I know nuttin, about the rain/ humidity affect on the casting of the boolit. I do a lot of casting outside under a roof, I don't cast when it is raining for obvious reasons. I do like the time after a rain when it is cool , humidity high? I can not prove or disprove anything, it is interesting to hear the different opinions/ findings.

I do most of my casting late morning, early afternoon, I get good fill out and don't have a lot of problems with the boolit bases...I don't like to make assumptions about things I can't back up, so , I'm following this conversation looking for the answer, If there is one.

[heebs]

Living in Minnesota, I have found that casting bullets in the cold (10 to -20) gives excellent results. I use a Magma caster. Relative humidity is nearly non-existant at that temp. I have given up try to make bullets at above 50 degrees. Molds don't cool. Maybe I am impatient, but when it gets above 40, it's time to do other things.

[Bret4207]

Now this is interesting. You won't find discussions like this at "Biily Joe Jim Bob's hardcast magnum shooters" web site.

I'm in the "fill rate and venting" crowd on this. To figure this out would take a lot of work with a few moulds and I doubt it'll be done.

[Dale53]

454PB;
>>>I quite lubing Lee moulds years ago. <<<

I agree with you about the problems associated with typical lubes recommended - mostly a bad idea.

However, using Bullshop's Sprue Plate lube (sparingly, of course) I have ALL of the benefits and NONE of the disadvantages previously "enjoyed" when using old lubing methods.

I will NEVER voluntarily go back to working without Bullshop's Sprue Plate lube on both my aluminum moulds and my iron moulds.

FWIW

Dale53

[leftiye]

Geez, I never had it cross my mind! I always cast indoors, and the humidity here is always below 30 percent. Maybe that's why. Seems there are several good reasons here why ambient conditions could affect casting. Several of these unavoidably must have some effect. I'm in the "it's all about heat" crowd. More heat in the mold/ melt, and rate of cooling.

[runfiverun]

i found that the humid condition will generally give me a slightly heavier boolit.
i keep a humidifier in the casting garage for the winter and a water evap cooler for the summer. for just this reason.

[JohnH]

I've no idea what effect rain has on casting, I only know that it's a good effect and I cast when it's raining whenever possible. I first read of this here soon after I joined up. Thought to myself Hmmmmmm..... Gave it a try and sure 'nuff, I was rewarded with a smoother casting session. I don't weigh sort, just a good eyeballing. I didn't notice a drop in reject rate, but filling was better and boolit color better, and there was an improvement of smoothness in the overall session. Lot's of times when casting, there are just annoying little things that happen. Sometimes it may be that lead splatters form on the mold block faces, sometimes lead smears on the block top/sprue plate. Sometimes it just seems that the timing of things is off just a tad and won't sequence up right no matter what you do. When it's raining, I just don't experience that stuff to the degree I do when it nice a clear. Go figure. I don't need to know the specifics of scientific explainations. It works and that's good enough for me. I'll leave the noodlin' to others.

[Mugs]

Being in AZ. there's not much humidity. I due most of my casting in the early morning when the humidity is the highest. I'm water droping all my boolits and that adds humidity to the casting area. I also agree 100% with Dale on Bullshops lube.
Mugs
IHMSA 5940L

[felix]

SlowElk, there is a definite answer, and one of these days I'll meet someone who can give me/us a clue so we can set up a valid experiment, time and attitude willing. The only problem is remembering this problem when someone who might know the physics of what we are talking about. To many other interesting things to talk about in such a short amount of time during a possible meeting. ... felix

[BeeMan]

Humid conditions...heavier bullets...that triggered a thought

The last session that resulted in the pinholes in the base also yielded lighter castings. I have been weighing boolits and looking at the weight distribution over several sessions now. The jury is still out on whether scores are any better, but that involves a bunch more variables. The worst of those is the nut behind the butt plate.

The last session was about 1 percent lighter than previous runs but the min to max spread was still about the same as before. Conditions were cool, dry, and windy. I cast in an open garage, just inside enough to be out of the wind. I was monitoring air temp and it was mid 60s about a 12 inches from the pot.

Forecast is 100 percent chance of rain here through the weekend, with slightly cooler temperatures than the last session. I see a chance to change only 1 or 2 variables, and watch for changes in 2 outcomes.

Air temp down slightly
Humidity way up
Bull plate lube, with and maybe without
Alloy temp, pot temp, and mold temp about the same

Watch for changes in pin holes, nominal weight, and distribution as usual.

Ignorance really was bliss when I lived in areas with much less variable weather than Northeast Oklahoma. If this shows a trend, I may have to invest in one of those electronic temperature / humidity meters. Need a barometer too. All in the name of possibly advancing our understanding of our hobby, of course.

BeeMan

[BeeMan]

Results from a short run this evening looked significantly better with regard to pinholes but it took a combination of changes to get there.

Air temp 72 was a foot from the pot in the partly open garage.
Humidity was about 90% per local weather stations, with damp driveway outside the door.
Virtually no breeze.
Bull plate sprue plate lube on all mold surfaces except in the cavities (same as before.)
Preheated RCBS 180FN on the hotplate.
WW alloy temp in the Lee 10 lb pot started about 740 per Lyman thermometer, dropping to just over 700 by the end.

Initial fills went back in the pot until the results were uniformly frosted, then castings were checked at each sprue cut and drop. The sprue was cut with a gloved hand to ensure uniform hardness at time of cut and minimal variation in tearout.

Pinholes were less but still there; more frequently on the second cavity being filled. From comments on fill rate, a reduced flow was tried next. This reduced the rate of pinholes by quite a bit more and the few left went back in the pot. The keepers will be weigh sorted next.

Rainy weather helped some, but I tend to credit the fill issue for the bigger improvement on this run. It will take more testing to draw any environmental conclusions but I'll call today progress.

BeeMan

[Randall]

I am in NE OK with rain all weekend,I cast some up on Saturday while it was raining and it seems like I can do no wrong casting with cool air and high humidty even with my troublesome moulds.

[sundog]

Beeman, Felix and I have batting this around for a long time. No doubt in my little ole pea brain that a condensing atmosphere offers the best casting opportunity. Due to humidity, it may have something to do with rate of cooling. Felix is right in one thing though. We need to find someone who is intimately familiar with the physics of the operation in order to set up correct experiment[s]. Otherwise, we're just kinda guessing.

You mentioned pinholes in bases. Had that problem once a few years ago and it ruined a day's worth of work. Discovered it by noticing a black spec on a base, and closer inspection revealed several hundred boolits almost all the same way. All went back to the pot. Same batch of alloy poured just fine the next time. And you mentioned that it was normally the second boolit poured. Did you try reversing pour order to eliminate cavity contamination?

Folks, y'all can all hoo-hoo this all ya want, but I am firmly convinced that different atmospheric conditions present different casting variables, and that a condensing atmosphere is one of, if not the best. I've had some days that even after a hunert or so boolits, they're all crap. All you can do is quit when that happens and try another day. Then the next day, everything being equal, they come out just great. Apparently not all things were equal.

[JSnover]

Funny. Years ago when I learned to TiG weld I was told "when the weather turns, your welds will turn to crap." But in my case, when the weather got bad the welds ran easier and filled better. Go figger.

[runfiverun]

corky i'm with you all the way on this one.
for my rifle stuff i get out the water everytime or wait for the rainy/snowy days.. for my pistol stuff it's whenever i have the chance. but theere is water in the air someway or another when i cast. period.
maybe thats why i have pretty consistent shiney boolits that are a bit harder.

[BeeMan]

Corky,

I first noticed the pinholes due to a dark speck just like you mentioned. I had cast what I thought was plenty for the April match and only saw the pinholes as I was weigh sorting a couple days later. Closer visual inspection resulted in about 40% rejects. Those culls went back into the pot this weekend.

The average weight of keepers from early April was about 1% lighter than normal for this mold but since they looked fine and the min to max weight distribution was typical I set them aside. When I got the specks to go away yesterday the weight was still 1% light.

Another run this afternoon gave results similar to yesterday's best as long as I filled the cavities at the slower rate. Filling cavities in the opposite order resulted in even fewer dark specks. The specks are only on the bases; the rest of the casting looks very clean.

We are in agreement that different environments create a new optimum balance of casting variables. Something here is giving new challenges I didn't encounter in NC. Since you and Felix have been tracking the regional WX factor for years I'll stack my odds based on your observations. It is puzzling though that fill rate and to a lesser degree fill order seemed to have more effect on eliminating specks / pinholes than the weather difference from April to this weekend.

Scott

[felix]

Scott, if any single boolit exhibits a hole that you can see within an acceptable lot of boolits, the entire lot is worthless and must be rejected. You can never assume the distribution of the holes are uniform throughout the boolit. If you want some "proof", rotate several in a tumbler and let them wear down some. Therefore, never do more than 20 boolits before a severe checkout for quality. Rule of thumb: 85% plus percent must hit EXACT weight (from same cavity, of course). However, any boolit is a good boolit for charging tin cans, especially during rapid fire using a lever gun. For a better percentage of hits, though, get bigger cans or shorten the distance for the usual sizes. ... felix