drop vase - strips separating when making blank

[seachange]

Hi

Have just made my very first drop vase, ½” thick blank, dropped 6”

I am happy with the results of the drop. However, I need to improve the blank.

The blank layout was

2x 1/8” Tekta base, ring mold size
2 layers of colored and tekta strips on top of this base. These are shorter than the width of the base.

I will cut off the blank, leaving just the vase shape. Therefore the colored strips are long enough to create thickness and pattern for the vase.
Top firing, did a full fuse.

The sets of 2x 1/8" strips - most pairs were 3/4" wide - moved fractionally apart during the full fuse. This created a tiny dip on the surface of the blank, in between 3 of the strip sets. To my surprise, this in turn left tiny ridges on the vase - I thought it would all dissapear during the drop. It also made a very thin line of diluted (almost clear) color between the strips.

Would like to keep the strips tightly together, so that the vase feels completely smooth all around, and the colors abut properly.

Firing the strips first, then flipping and re-firing on top of the tekta bases would probably work, but adds another (a 3rd) firing cycle.
In my kiln this is at least another 30 hours until everything is cold enough.

Can’t place a dam around the strips, because the tekta base is bigger than the strips.

Have thought about this layout instead:

1x 1/8” Tekta base, mold size (instead of 2 layers)
2 layers of strips
1x tekta square piece on top, covering all the strips.

Do you think the square piece of tekta on top of the strips will help to keep the strips together?

It is probably silly, but it is the first time I am working with 4 layers, and can’t quite picture if the tekta on top will do what I want, or do the opposite, the weight of the glass increasing the movement - and separation - of the strips below it.

This layout would most probably not leave a ridge, but, if the colors are separated, the line of diluted color in between the strips would still be there.

Many thanks for your help, seachange

[Lauri Levanto]

My uneducated guess is that your strips were opaque. many opaque glasses are more viscose that clear glass. During the drop gravity pulls the glass gown. The softer Tekta gives more and this may cause full separation of the stiffer strips, leaving a clear line between. There may be a difference
-- if the soft Tekla lays upon stiffer glass (= strips on outside), or
- thestrips ride on the Tekta (=strips inside)

I have made drop vases with a design where every second strip is transparent.
These develop wider , and therefore thinner, than the colored ones.

-lauri

[seachange]

My uneducated guess is that your strips were opaque. many opaque glasses are more viscose that clear glass. During the drop gravity pulls the glass gown. The softer Tekta gives more and this may cause full separation of the stiffer strips, leaving a clear line between. There may be a difference
-- if the soft Tekla lays upon stiffer glass (= strips on outside), or
- thestrips ride on the Tekta (=strips inside)

I have made drop vases with a design where every second strip is transparent.
These develop wider , and therefore thinner, than the colored ones.

-lauri

Hi Lauri

Many thanks for your response. In this case all the strips were transparent. However, the point you explained regarding the different viscosities and spreading is very interesting, could perhaps result in designs with thin borders in between without having to cut extra thin strips.

After I posted, it ocurred to me that may be I hadn't fully fused? It did look all even and flat in the kiln, but when it cooled down I discovered the thin ridges in between the strips. May be the glass was after all not hot enough?

I will make another blank and fire hotter, to make sure it is really even. This might help with the ridges, but still won't solve the problem of the the diluted line visible between the colored strips.

Intend to use mainly transparent glass, hopefully someone has a suggestion about how to keep those strips nicely together. It keeps turning in my head, but can't picture what to do.

Thanks again, seachange

[ejgiebel]

I think you are seeing two different issues. If you fire strips on top of a clear blank, the clear will usually "float" up in the seam. You really see this when the opaque seams don't butt really tight. You'd think the top color would spread out, but it's more like it settles down and the clear fills in the seams. It's one of the reasons I rarely create a two layer piece with an opaque top using a clear base. So the color density in the seam will be less than elsewhere. Only thing that would help would be to pre-fire the colored pieces into a single piece, and then put this on the clear pieces and fuse again.

The other issue, as Lauri mentioned, has to do with the absorbtion of heat by the different colors. I've never had a drop vase that was "as smooth as glass". The different colors absorb different amounts of heat, they flow (stretch) differently, and in general do not create the perfectly smooth surface one might be able to achieve if blowing the glass.

As a comparison, I have done some pot melts, 1/2 thick, and then draped them over a stainless steel floral former. I started with a 14 inch circle, and the resulting vase is 11 inches tall with a 3 inch base, so it stretched about 5.5 inches. The texture on the glass is easily visible in room light, and you can feel the texture on the surface of the piece. The piece that was draped was perfectly smooth, but the resulting piece shows texture from the way the various colors flowed. The drape was down at 1225 F, and it only took 15 minutes at that temp.

Ed

[seachange]

Hi Ed

many thanks for your detailed reply. I am starting to understand the factors that come into play with the different viscosities. Also to see what a full fuse is...I should probably have posted this query in the newcomers section, working this thick is a new experience for me.

Then I have never seen a drop vase in person (only blown ones), so was assuming that they were perfectly smooth. Your explanation and example of your drape vase makes sense to me.

I like the results, even like the process, though it is rather long, so will be making several smaller vases to test colors. Planning to use 3.5" ID with 3 layers for a 10" drop, hoping to learn lots from all these tests.

Thanks again for your help, have another one in the kiln right now. Fused the blank hotter, but still not quite enough...the next one should be all right
Best regards, seachange

[David Jenkins]

I don't have a lot of experience on this, but I'm thinking you'll have a difficult time dropping three layers 10". My guess would be that you'll stretch the blank so thin you'll get holes. I seem to remember a heuristic that says you can drop 1" for the first 2 layers, and then an additional 2" for each additional layer. That would say you might be able to manage a 4 1/2" - 5" drop. I'm not sure how, or if, the diameter or geometry of the hole plays into that.

Others will chime in, I'm sure. Let us know how it came out and maybe provide a picture?

Edited: Dusting off my HS algebra, I'm thinking the dropped vase thickness will vary inversely with the square of the radius of the hole (assuming a round hole). And that ignores whatever happens at the bottom. (But HS was a long, long time ago. )

[seachange]

I don't have a lot of experience on this, but I'm thinking you'll have a difficult time dropping three layers 10". My guess would be that you'll stretch the blank so thin you'll get holes. I seem to remember a heuristic that says you can drop 1" for the first 2 layers, and then an additional 2" for each additional layer. That would say you might be able to manage a 4 1/2" - 5" drop. I'm not sure how, or if, the diameter or geometry of the hole plays into that.

Others will chime in, I'm sure. Let us know how it came out and maybe provide a picture?

Edited: Dusting off my HS algebra, I'm thinking the dropped vase thickness will vary inversely with the square of the radius of the hole (assuming a round hole). And that ignores whatever happens at the bottom. (But HS was a long, long time ago. )

Hi David, you are correct, time hasn't had any effect . I work in centimeters, so was thinking 10cm, which is 4", with 3 layers of glass (not the 10" I wrote). It is annealing now, dropped a bit more than I wanted. The peep hole in the kiln is not in the right position for drop vases. It is amazing how quickly it can go in the last 1 to 3 minutes.

My first try was 6" 15cm, with 4 layers. This seems to have worked very well, but I still have to cut the top of the vase off, hoping to do this within the next couple of weeks. Then I'll be able to see better the thickness at the top.

Many thanks, seachange