White is not a color that is available in the sublimation dye print process.
This is why the majority (but not all) of sublimatable products will have a white coating, which serves as the white background that the color dye is transferred to.
The products that do not have a white base color (stainless steel, glassware, burlap, etc), are not able to be printed with white-base color.
Any user-provided artwork files will not be able to be printed with any whites in the final product.
Because of this, the live preview/design proofs that you see and/or save from within the customizer may not be representative of the finished product, depending on which product is customized.
White colors are retained in our off-the-shelf sub dye artwork, so that customers can properly build up designs, using the provided design elements.
We encourage customers ordering sub dye products to reach out with any questions they may have about their artwork, and how it will appear in the finished product.